diff --git a/src/heap/spaces.h b/src/heap/spaces.h
new file mode 100644
index 0000000..9ecb3c4
--- /dev/null
+++ b/src/heap/spaces.h
@@ -0,0 +1,2886 @@
+// Copyright 2011 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_HEAP_SPACES_H_
+#define V8_HEAP_SPACES_H_
+
+#include "src/allocation.h"
+#include "src/base/atomicops.h"
+#include "src/base/bits.h"
+#include "src/base/platform/mutex.h"
+#include "src/hashmap.h"
+#include "src/list.h"
+#include "src/log.h"
+#include "src/utils.h"
+
+namespace v8 {
+namespace internal {
+
+class Isolate;
+
+// -----------------------------------------------------------------------------
+// Heap structures:
+//
+// A JS heap consists of a young generation, an old generation, and a large
+// object space. The young generation is divided into two semispaces. A
+// scavenger implements Cheney's copying algorithm. The old generation is
+// separated into a map space and an old object space. The map space contains
+// all (and only) map objects, the rest of old objects go into the old space.
+// The old generation is collected by a mark-sweep-compact collector.
+//
+// The semispaces of the young generation are contiguous.  The old and map
+// spaces consists of a list of pages. A page has a page header and an object
+// area.
+//
+// There is a separate large object space for objects larger than
+// Page::kMaxHeapObjectSize, so that they do not have to move during
+// collection. The large object space is paged. Pages in large object space
+// may be larger than the page size.
+//
+// A store-buffer based write barrier is used to keep track of intergenerational
+// references.  See heap/store-buffer.h.
+//
+// During scavenges and mark-sweep collections we sometimes (after a store
+// buffer overflow) iterate intergenerational pointers without decoding heap
+// object maps so if the page belongs to old pointer space or large object
+// space it is essential to guarantee that the page does not contain any
+// garbage pointers to new space: every pointer aligned word which satisfies
+// the Heap::InNewSpace() predicate must be a pointer to a live heap object in
+// new space. Thus objects in old pointer and large object spaces should have a
+// special layout (e.g. no bare integer fields). This requirement does not
+// apply to map space which is iterated in a special fashion. However we still
+// require pointer fields of dead maps to be cleaned.
+//
+// To enable lazy cleaning of old space pages we can mark chunks of the page
+// as being garbage.  Garbage sections are marked with a special map.  These
+// sections are skipped when scanning the page, even if we are otherwise
+// scanning without regard for object boundaries.  Garbage sections are chained
+// together to form a free list after a GC.  Garbage sections created outside
+// of GCs by object trunctation etc. may not be in the free list chain.  Very
+// small free spaces are ignored, they need only be cleaned of bogus pointers
+// into new space.
+//
+// Each page may have up to one special garbage section.  The start of this
+// section is denoted by the top field in the space.  The end of the section
+// is denoted by the limit field in the space.  This special garbage section
+// is not marked with a free space map in the data.  The point of this section
+// is to enable linear allocation without having to constantly update the byte
+// array every time the top field is updated and a new object is created.  The
+// special garbage section is not in the chain of garbage sections.
+//
+// Since the top and limit fields are in the space, not the page, only one page
+// has a special garbage section, and if the top and limit are equal then there
+// is no special garbage section.
+
+// Some assertion macros used in the debugging mode.
+
+#define DCHECK_PAGE_ALIGNED(address) \
+  DCHECK((OffsetFrom(address) & Page::kPageAlignmentMask) == 0)
+
+#define DCHECK_OBJECT_ALIGNED(address) \
+  DCHECK((OffsetFrom(address) & kObjectAlignmentMask) == 0)
+
+#define DCHECK_OBJECT_SIZE(size) \
+  DCHECK((0 < size) && (size <= Page::kMaxRegularHeapObjectSize))
+
+#define DCHECK_PAGE_OFFSET(offset) \
+  DCHECK((Page::kObjectStartOffset <= offset) && (offset <= Page::kPageSize))
+
+#define DCHECK_MAP_PAGE_INDEX(index) \
+  DCHECK((0 <= index) && (index <= MapSpace::kMaxMapPageIndex))
+
+
+class PagedSpace;
+class MemoryAllocator;
+class AllocationInfo;
+class Space;
+class FreeList;
+class MemoryChunk;
+
+class MarkBit {
+ public:
+  typedef uint32_t CellType;
+
+  inline MarkBit(CellType* cell, CellType mask, bool data_only)
+      : cell_(cell), mask_(mask), data_only_(data_only) {}
+
+  inline CellType* cell() { return cell_; }
+  inline CellType mask() { return mask_; }
+
+#ifdef DEBUG
+  bool operator==(const MarkBit& other) {
+    return cell_ == other.cell_ && mask_ == other.mask_;
+  }
+#endif
+
+  inline void Set() { *cell_ |= mask_; }
+  inline bool Get() { return (*cell_ & mask_) != 0; }
+  inline void Clear() { *cell_ &= ~mask_; }
+
+  inline bool data_only() { return data_only_; }
+
+  inline MarkBit Next() {
+    CellType new_mask = mask_ << 1;
+    if (new_mask == 0) {
+      return MarkBit(cell_ + 1, 1, data_only_);
+    } else {
+      return MarkBit(cell_, new_mask, data_only_);
+    }
+  }
+
+ private:
+  CellType* cell_;
+  CellType mask_;
+  // This boolean indicates that the object is in a data-only space with no
+  // pointers.  This enables some optimizations when marking.
+  // It is expected that this field is inlined and turned into control flow
+  // at the place where the MarkBit object is created.
+  bool data_only_;
+};
+
+
+// Bitmap is a sequence of cells each containing fixed number of bits.
+class Bitmap {
+ public:
+  static const uint32_t kBitsPerCell = 32;
+  static const uint32_t kBitsPerCellLog2 = 5;
+  static const uint32_t kBitIndexMask = kBitsPerCell - 1;
+  static const uint32_t kBytesPerCell = kBitsPerCell / kBitsPerByte;
+  static const uint32_t kBytesPerCellLog2 = kBitsPerCellLog2 - kBitsPerByteLog2;
+
+  static const size_t kLength = (1 << kPageSizeBits) >> (kPointerSizeLog2);
+
+  static const size_t kSize =
+      (1 << kPageSizeBits) >> (kPointerSizeLog2 + kBitsPerByteLog2);
+
+
+  static int CellsForLength(int length) {
+    return (length + kBitsPerCell - 1) >> kBitsPerCellLog2;
+  }
+
+  int CellsCount() { return CellsForLength(kLength); }
+
+  static int SizeFor(int cells_count) {
+    return sizeof(MarkBit::CellType) * cells_count;
+  }
+
+  INLINE(static uint32_t IndexToCell(uint32_t index)) {
+    return index >> kBitsPerCellLog2;
+  }
+
+  INLINE(static uint32_t CellToIndex(uint32_t index)) {
+    return index << kBitsPerCellLog2;
+  }
+
+  INLINE(static uint32_t CellAlignIndex(uint32_t index)) {
+    return (index + kBitIndexMask) & ~kBitIndexMask;
+  }
+
+  INLINE(MarkBit::CellType* cells()) {
+    return reinterpret_cast<MarkBit::CellType*>(this);
+  }
+
+  INLINE(Address address()) { return reinterpret_cast<Address>(this); }
+
+  INLINE(static Bitmap* FromAddress(Address addr)) {
+    return reinterpret_cast<Bitmap*>(addr);
+  }
+
+  inline MarkBit MarkBitFromIndex(uint32_t index, bool data_only = false) {
+    MarkBit::CellType mask = 1 << (index & kBitIndexMask);
+    MarkBit::CellType* cell = this->cells() + (index >> kBitsPerCellLog2);
+    return MarkBit(cell, mask, data_only);
+  }
+
+  static inline void Clear(MemoryChunk* chunk);
+
+  static void PrintWord(uint32_t word, uint32_t himask = 0) {
+    for (uint32_t mask = 1; mask != 0; mask <<= 1) {
+      if ((mask & himask) != 0) PrintF("[");
+      PrintF((mask & word) ? "1" : "0");
+      if ((mask & himask) != 0) PrintF("]");
+    }
+  }
+
+  class CellPrinter {
+   public:
+    CellPrinter() : seq_start(0), seq_type(0), seq_length(0) {}
+
+    void Print(uint32_t pos, uint32_t cell) {
+      if (cell == seq_type) {
+        seq_length++;
+        return;
+      }
+
+      Flush();
+
+      if (IsSeq(cell)) {
+        seq_start = pos;
+        seq_length = 0;
+        seq_type = cell;
+        return;
+      }
+
+      PrintF("%d: ", pos);
+      PrintWord(cell);
+      PrintF("\n");
+    }
+
+    void Flush() {
+      if (seq_length > 0) {
+        PrintF("%d: %dx%d\n", seq_start, seq_type == 0 ? 0 : 1,
+               seq_length * kBitsPerCell);
+        seq_length = 0;
+      }
+    }
+
+    static bool IsSeq(uint32_t cell) { return cell == 0 || cell == 0xFFFFFFFF; }
+
+   private:
+    uint32_t seq_start;
+    uint32_t seq_type;
+    uint32_t seq_length;
+  };
+
+  void Print() {
+    CellPrinter printer;
+    for (int i = 0; i < CellsCount(); i++) {
+      printer.Print(i, cells()[i]);
+    }
+    printer.Flush();
+    PrintF("\n");
+  }
+
+  bool IsClean() {
+    for (int i = 0; i < CellsCount(); i++) {
+      if (cells()[i] != 0) {
+        return false;
+      }
+    }
+    return true;
+  }
+};
+
+
+class SkipList;
+class SlotsBuffer;
+
+// MemoryChunk represents a memory region owned by a specific space.
+// It is divided into the header and the body. Chunk start is always
+// 1MB aligned. Start of the body is aligned so it can accommodate
+// any heap object.
+class MemoryChunk {
+ public:
+  // Only works if the pointer is in the first kPageSize of the MemoryChunk.
+  static MemoryChunk* FromAddress(Address a) {
+    return reinterpret_cast<MemoryChunk*>(OffsetFrom(a) & ~kAlignmentMask);
+  }
+  static const MemoryChunk* FromAddress(const byte* a) {
+    return reinterpret_cast<const MemoryChunk*>(OffsetFrom(a) &
+                                                ~kAlignmentMask);
+  }
+
+  // Only works for addresses in pointer spaces, not data or code spaces.
+  static inline MemoryChunk* FromAnyPointerAddress(Heap* heap, Address addr);
+
+  Address address() { return reinterpret_cast<Address>(this); }
+
+  bool is_valid() { return address() != NULL; }
+
+  MemoryChunk* next_chunk() const {
+    return reinterpret_cast<MemoryChunk*>(base::Acquire_Load(&next_chunk_));
+  }
+
+  MemoryChunk* prev_chunk() const {
+    return reinterpret_cast<MemoryChunk*>(base::Acquire_Load(&prev_chunk_));
+  }
+
+  void set_next_chunk(MemoryChunk* next) {
+    base::Release_Store(&next_chunk_, reinterpret_cast<base::AtomicWord>(next));
+  }
+
+  void set_prev_chunk(MemoryChunk* prev) {
+    base::Release_Store(&prev_chunk_, reinterpret_cast<base::AtomicWord>(prev));
+  }
+
+  Space* owner() const {
+    if ((reinterpret_cast<intptr_t>(owner_) & kPageHeaderTagMask) ==
+        kPageHeaderTag) {
+      return reinterpret_cast<Space*>(reinterpret_cast<intptr_t>(owner_) -
+                                      kPageHeaderTag);
+    } else {
+      return NULL;
+    }
+  }
+
+  void set_owner(Space* space) {
+    DCHECK((reinterpret_cast<intptr_t>(space) & kPageHeaderTagMask) == 0);
+    owner_ = reinterpret_cast<Address>(space) + kPageHeaderTag;
+    DCHECK((reinterpret_cast<intptr_t>(owner_) & kPageHeaderTagMask) ==
+           kPageHeaderTag);
+  }
+
+  base::VirtualMemory* reserved_memory() { return &reservation_; }
+
+  void InitializeReservedMemory() { reservation_.Reset(); }
+
+  void set_reserved_memory(base::VirtualMemory* reservation) {
+    DCHECK_NOT_NULL(reservation);
+    reservation_.TakeControl(reservation);
+  }
+
+  bool scan_on_scavenge() { return IsFlagSet(SCAN_ON_SCAVENGE); }
+  void initialize_scan_on_scavenge(bool scan) {
+    if (scan) {
+      SetFlag(SCAN_ON_SCAVENGE);
+    } else {
+      ClearFlag(SCAN_ON_SCAVENGE);
+    }
+  }
+  inline void set_scan_on_scavenge(bool scan);
+
+  int store_buffer_counter() { return store_buffer_counter_; }
+  void set_store_buffer_counter(int counter) {
+    store_buffer_counter_ = counter;
+  }
+
+  bool Contains(Address addr) {
+    return addr >= area_start() && addr < area_end();
+  }
+
+  // Checks whether addr can be a limit of addresses in this page.
+  // It's a limit if it's in the page, or if it's just after the
+  // last byte of the page.
+  bool ContainsLimit(Address addr) {
+    return addr >= area_start() && addr <= area_end();
+  }
+
+  // Every n write barrier invocations we go to runtime even though
+  // we could have handled it in generated code.  This lets us check
+  // whether we have hit the limit and should do some more marking.
+  static const int kWriteBarrierCounterGranularity = 500;
+
+  enum MemoryChunkFlags {
+    IS_EXECUTABLE,
+    ABOUT_TO_BE_FREED,
+    POINTERS_TO_HERE_ARE_INTERESTING,
+    POINTERS_FROM_HERE_ARE_INTERESTING,
+    SCAN_ON_SCAVENGE,
+    IN_FROM_SPACE,  // Mutually exclusive with IN_TO_SPACE.
+    IN_TO_SPACE,    // All pages in new space has one of these two set.
+    NEW_SPACE_BELOW_AGE_MARK,
+    CONTAINS_ONLY_DATA,
+    EVACUATION_CANDIDATE,
+    RESCAN_ON_EVACUATION,
+
+    // WAS_SWEPT indicates that marking bits have been cleared by the sweeper,
+    // otherwise marking bits are still intact.
+    WAS_SWEPT,
+
+    // Large objects can have a progress bar in their page header. These object
+    // are scanned in increments and will be kept black while being scanned.
+    // Even if the mutator writes to them they will be kept black and a white
+    // to grey transition is performed in the value.
+    HAS_PROGRESS_BAR,
+
+    // Last flag, keep at bottom.
+    NUM_MEMORY_CHUNK_FLAGS
+  };
+
+
+  static const int kPointersToHereAreInterestingMask =
+      1 << POINTERS_TO_HERE_ARE_INTERESTING;
+
+  static const int kPointersFromHereAreInterestingMask =
+      1 << POINTERS_FROM_HERE_ARE_INTERESTING;
+
+  static const int kEvacuationCandidateMask = 1 << EVACUATION_CANDIDATE;
+
+  static const int kSkipEvacuationSlotsRecordingMask =
+      (1 << EVACUATION_CANDIDATE) | (1 << RESCAN_ON_EVACUATION) |
+      (1 << IN_FROM_SPACE) | (1 << IN_TO_SPACE);
+
+
+  void SetFlag(int flag) { flags_ |= static_cast<uintptr_t>(1) << flag; }
+
+  void ClearFlag(int flag) { flags_ &= ~(static_cast<uintptr_t>(1) << flag); }
+
+  void SetFlagTo(int flag, bool value) {
+    if (value) {
+      SetFlag(flag);
+    } else {
+      ClearFlag(flag);
+    }
+  }
+
+  bool IsFlagSet(int flag) {
+    return (flags_ & (static_cast<uintptr_t>(1) << flag)) != 0;
+  }
+
+  // Set or clear multiple flags at a time. The flags in the mask
+  // are set to the value in "flags", the rest retain the current value
+  // in flags_.
+  void SetFlags(intptr_t flags, intptr_t mask) {
+    flags_ = (flags_ & ~mask) | (flags & mask);
+  }
+
+  // Return all current flags.
+  intptr_t GetFlags() { return flags_; }
+
+
+  // SWEEPING_DONE - The page state when sweeping is complete or sweeping must
+  // not be performed on that page.
+  // SWEEPING_FINALIZE - A sweeper thread is done sweeping this page and will
+  // not touch the page memory anymore.
+  // SWEEPING_IN_PROGRESS - This page is currently swept by a sweeper thread.
+  // SWEEPING_PENDING - This page is ready for parallel sweeping.
+  enum ParallelSweepingState {
+    SWEEPING_DONE,
+    SWEEPING_FINALIZE,
+    SWEEPING_IN_PROGRESS,
+    SWEEPING_PENDING
+  };
+
+  ParallelSweepingState parallel_sweeping() {
+    return static_cast<ParallelSweepingState>(
+        base::Acquire_Load(&parallel_sweeping_));
+  }
+
+  void set_parallel_sweeping(ParallelSweepingState state) {
+    base::Release_Store(&parallel_sweeping_, state);
+  }
+
+  bool TryParallelSweeping() {
+    return base::Acquire_CompareAndSwap(&parallel_sweeping_, SWEEPING_PENDING,
+                                        SWEEPING_IN_PROGRESS) ==
+           SWEEPING_PENDING;
+  }
+
+  bool SweepingCompleted() { return parallel_sweeping() <= SWEEPING_FINALIZE; }
+
+  // Manage live byte count (count of bytes known to be live,
+  // because they are marked black).
+  void ResetLiveBytes() {
+    if (FLAG_gc_verbose) {
+      PrintF("ResetLiveBytes:%p:%x->0\n", static_cast<void*>(this),
+             live_byte_count_);
+    }
+    live_byte_count_ = 0;
+  }
+  void IncrementLiveBytes(int by) {
+    if (FLAG_gc_verbose) {
+      printf("UpdateLiveBytes:%p:%x%c=%x->%x\n", static_cast<void*>(this),
+             live_byte_count_, ((by < 0) ? '-' : '+'), ((by < 0) ? -by : by),
+             live_byte_count_ + by);
+    }
+    live_byte_count_ += by;
+    DCHECK_LE(static_cast<unsigned>(live_byte_count_), size_);
+  }
+  int LiveBytes() {
+    DCHECK(static_cast<unsigned>(live_byte_count_) <= size_);
+    return live_byte_count_;
+  }
+
+  int write_barrier_counter() {
+    return static_cast<int>(write_barrier_counter_);
+  }
+
+  void set_write_barrier_counter(int counter) {
+    write_barrier_counter_ = counter;
+  }
+
+  int progress_bar() {
+    DCHECK(IsFlagSet(HAS_PROGRESS_BAR));
+    return progress_bar_;
+  }
+
+  void set_progress_bar(int progress_bar) {
+    DCHECK(IsFlagSet(HAS_PROGRESS_BAR));
+    progress_bar_ = progress_bar;
+  }
+
+  void ResetProgressBar() {
+    if (IsFlagSet(MemoryChunk::HAS_PROGRESS_BAR)) {
+      set_progress_bar(0);
+      ClearFlag(MemoryChunk::HAS_PROGRESS_BAR);
+    }
+  }
+
+  bool IsLeftOfProgressBar(Object** slot) {
+    Address slot_address = reinterpret_cast<Address>(slot);
+    DCHECK(slot_address > this->address());
+    return (slot_address - (this->address() + kObjectStartOffset)) <
+           progress_bar();
+  }
+
+  static void IncrementLiveBytesFromGC(Address address, int by) {
+    MemoryChunk::FromAddress(address)->IncrementLiveBytes(by);
+  }
+
+  static void IncrementLiveBytesFromMutator(Address address, int by);
+
+  static const intptr_t kAlignment =
+      (static_cast<uintptr_t>(1) << kPageSizeBits);
+
+  static const intptr_t kAlignmentMask = kAlignment - 1;
+
+  static const intptr_t kSizeOffset = 0;
+
+  static const intptr_t kLiveBytesOffset =
+      kSizeOffset + kPointerSize + kPointerSize + kPointerSize + kPointerSize +
+      kPointerSize + kPointerSize + kPointerSize + kPointerSize + kIntSize;
+
+  static const size_t kSlotsBufferOffset = kLiveBytesOffset + kIntSize;
+
+  static const size_t kWriteBarrierCounterOffset =
+      kSlotsBufferOffset + kPointerSize + kPointerSize;
+
+  static const size_t kHeaderSize =
+      kWriteBarrierCounterOffset + kPointerSize + kIntSize + kIntSize +
+      kPointerSize + 5 * kPointerSize + kPointerSize + kPointerSize;
+
+  static const int kBodyOffset =
+      CODE_POINTER_ALIGN(kHeaderSize + Bitmap::kSize);
+
+  // The start offset of the object area in a page. Aligned to both maps and
+  // code alignment to be suitable for both.  Also aligned to 32 words because
+  // the marking bitmap is arranged in 32 bit chunks.
+  static const int kObjectStartAlignment = 32 * kPointerSize;
+  static const int kObjectStartOffset =
+      kBodyOffset - 1 +
+      (kObjectStartAlignment - (kBodyOffset - 1) % kObjectStartAlignment);
+
+  size_t size() const { return size_; }
+
+  void set_size(size_t size) { size_ = size; }
+
+  void SetArea(Address area_start, Address area_end) {
+    area_start_ = area_start;
+    area_end_ = area_end;
+  }
+
+  Executability executable() {
+    return IsFlagSet(IS_EXECUTABLE) ? EXECUTABLE : NOT_EXECUTABLE;
+  }
+
+  bool ContainsOnlyData() { return IsFlagSet(CONTAINS_ONLY_DATA); }
+
+  bool InNewSpace() {
+    return (flags_ & ((1 << IN_FROM_SPACE) | (1 << IN_TO_SPACE))) != 0;
+  }
+
+  bool InToSpace() { return IsFlagSet(IN_TO_SPACE); }
+
+  bool InFromSpace() { return IsFlagSet(IN_FROM_SPACE); }
+
+  // ---------------------------------------------------------------------
+  // Markbits support
+
+  inline Bitmap* markbits() {
+    return Bitmap::FromAddress(address() + kHeaderSize);
+  }
+
+  void PrintMarkbits() { markbits()->Print(); }
+
+  inline uint32_t AddressToMarkbitIndex(Address addr) {
+    return static_cast<uint32_t>(addr - this->address()) >> kPointerSizeLog2;
+  }
+
+  inline static uint32_t FastAddressToMarkbitIndex(Address addr) {
+    const intptr_t offset = reinterpret_cast<intptr_t>(addr) & kAlignmentMask;
+
+    return static_cast<uint32_t>(offset) >> kPointerSizeLog2;
+  }
+
+  inline Address MarkbitIndexToAddress(uint32_t index) {
+    return this->address() + (index << kPointerSizeLog2);
+  }
+
+  void InsertAfter(MemoryChunk* other);
+  void Unlink();
+
+  inline Heap* heap() const { return heap_; }
+
+  static const int kFlagsOffset = kPointerSize;
+
+  bool IsEvacuationCandidate() { return IsFlagSet(EVACUATION_CANDIDATE); }
+
+  bool ShouldSkipEvacuationSlotRecording() {
+    return (flags_ & kSkipEvacuationSlotsRecordingMask) != 0;
+  }
+
+  inline SkipList* skip_list() { return skip_list_; }
+
+  inline void set_skip_list(SkipList* skip_list) { skip_list_ = skip_list; }
+
+  inline SlotsBuffer* slots_buffer() { return slots_buffer_; }
+
+  inline SlotsBuffer** slots_buffer_address() { return &slots_buffer_; }
+
+  void MarkEvacuationCandidate() {
+    DCHECK(slots_buffer_ == NULL);
+    SetFlag(EVACUATION_CANDIDATE);
+  }
+
+  void ClearEvacuationCandidate() {
+    DCHECK(slots_buffer_ == NULL);
+    ClearFlag(EVACUATION_CANDIDATE);
+  }
+
+  Address area_start() { return area_start_; }
+  Address area_end() { return area_end_; }
+  int area_size() { return static_cast<int>(area_end() - area_start()); }
+  bool CommitArea(size_t requested);
+
+  // Approximate amount of physical memory committed for this chunk.
+  size_t CommittedPhysicalMemory() { return high_water_mark_; }
+
+  static inline void UpdateHighWaterMark(Address mark);
+
+ protected:
+  size_t size_;
+  intptr_t flags_;
+
+  // Start and end of allocatable memory on this chunk.
+  Address area_start_;
+  Address area_end_;
+
+  // If the chunk needs to remember its memory reservation, it is stored here.
+  base::VirtualMemory reservation_;
+  // The identity of the owning space.  This is tagged as a failure pointer, but
+  // no failure can be in an object, so this can be distinguished from any entry
+  // in a fixed array.
+  Address owner_;
+  Heap* heap_;
+  // Used by the store buffer to keep track of which pages to mark scan-on-
+  // scavenge.
+  int store_buffer_counter_;
+  // Count of bytes marked black on page.
+  int live_byte_count_;
+  SlotsBuffer* slots_buffer_;
+  SkipList* skip_list_;
+  intptr_t write_barrier_counter_;
+  // Used by the incremental marker to keep track of the scanning progress in
+  // large objects that have a progress bar and are scanned in increments.
+  int progress_bar_;
+  // Assuming the initial allocation on a page is sequential,
+  // count highest number of bytes ever allocated on the page.
+  int high_water_mark_;
+
+  base::AtomicWord parallel_sweeping_;
+
+  // PagedSpace free-list statistics.
+  intptr_t available_in_small_free_list_;
+  intptr_t available_in_medium_free_list_;
+  intptr_t available_in_large_free_list_;
+  intptr_t available_in_huge_free_list_;
+  intptr_t non_available_small_blocks_;
+
+  static MemoryChunk* Initialize(Heap* heap, Address base, size_t size,
+                                 Address area_start, Address area_end,
+                                 Executability executable, Space* owner);
+
+ private:
+  // next_chunk_ holds a pointer of type MemoryChunk
+  base::AtomicWord next_chunk_;
+  // prev_chunk_ holds a pointer of type MemoryChunk
+  base::AtomicWord prev_chunk_;
+
+  friend class MemoryAllocator;
+};
+
+
+STATIC_ASSERT(sizeof(MemoryChunk) <= MemoryChunk::kHeaderSize);
+
+
+// -----------------------------------------------------------------------------
+// A page is a memory chunk of a size 1MB. Large object pages may be larger.
+//
+// The only way to get a page pointer is by calling factory methods:
+//   Page* p = Page::FromAddress(addr); or
+//   Page* p = Page::FromAllocationTop(top);
+class Page : public MemoryChunk {
+ public:
+  // Returns the page containing a given address. The address ranges
+  // from [page_addr .. page_addr + kPageSize[
+  // This only works if the object is in fact in a page.  See also MemoryChunk::
+  // FromAddress() and FromAnyAddress().
+  INLINE(static Page* FromAddress(Address a)) {
+    return reinterpret_cast<Page*>(OffsetFrom(a) & ~kPageAlignmentMask);
+  }
+
+  // Returns the page containing an allocation top. Because an allocation
+  // top address can be the upper bound of the page, we need to subtract
+  // it with kPointerSize first. The address ranges from
+  // [page_addr + kObjectStartOffset .. page_addr + kPageSize].
+  INLINE(static Page* FromAllocationTop(Address top)) {
+    Page* p = FromAddress(top - kPointerSize);
+    return p;
+  }
+
+  // Returns the next page in the chain of pages owned by a space.
+  inline Page* next_page();
+  inline Page* prev_page();
+  inline void set_next_page(Page* page);
+  inline void set_prev_page(Page* page);
+
+  // Checks whether an address is page aligned.
+  static bool IsAlignedToPageSize(Address a) {
+    return 0 == (OffsetFrom(a) & kPageAlignmentMask);
+  }
+
+  // Returns the offset of a given address to this page.
+  INLINE(int Offset(Address a)) {
+    int offset = static_cast<int>(a - address());
+    return offset;
+  }
+
+  // Returns the address for a given offset to the this page.
+  Address OffsetToAddress(int offset) {
+    DCHECK_PAGE_OFFSET(offset);
+    return address() + offset;
+  }
+
+  // ---------------------------------------------------------------------
+
+  // Page size in bytes.  This must be a multiple of the OS page size.
+  static const int kPageSize = 1 << kPageSizeBits;
+
+  // Maximum object size that fits in a page. Objects larger than that size
+  // are allocated in large object space and are never moved in memory. This
+  // also applies to new space allocation, since objects are never migrated
+  // from new space to large object space.  Takes double alignment into account.
+  static const int kMaxRegularHeapObjectSize = kPageSize - kObjectStartOffset;
+
+  // Page size mask.
+  static const intptr_t kPageAlignmentMask = (1 << kPageSizeBits) - 1;
+
+  inline void ClearGCFields();
+
+  static inline Page* Initialize(Heap* heap, MemoryChunk* chunk,
+                                 Executability executable, PagedSpace* owner);
+
+  void InitializeAsAnchor(PagedSpace* owner);
+
+  bool WasSwept() { return IsFlagSet(WAS_SWEPT); }
+  void SetWasSwept() { SetFlag(WAS_SWEPT); }
+  void ClearWasSwept() { ClearFlag(WAS_SWEPT); }
+
+  void ResetFreeListStatistics();
+
+#define FRAGMENTATION_STATS_ACCESSORS(type, name) \
+  type name() { return name##_; }                 \
+  void set_##name(type name) { name##_ = name; }  \
+  void add_##name(type name) { name##_ += name; }
+
+  FRAGMENTATION_STATS_ACCESSORS(intptr_t, non_available_small_blocks)
+  FRAGMENTATION_STATS_ACCESSORS(intptr_t, available_in_small_free_list)
+  FRAGMENTATION_STATS_ACCESSORS(intptr_t, available_in_medium_free_list)
+  FRAGMENTATION_STATS_ACCESSORS(intptr_t, available_in_large_free_list)
+  FRAGMENTATION_STATS_ACCESSORS(intptr_t, available_in_huge_free_list)
+
+#undef FRAGMENTATION_STATS_ACCESSORS
+
+#ifdef DEBUG
+  void Print();
+#endif  // DEBUG
+
+  friend class MemoryAllocator;
+};
+
+
+STATIC_ASSERT(sizeof(Page) <= MemoryChunk::kHeaderSize);
+
+
+class LargePage : public MemoryChunk {
+ public:
+  HeapObject* GetObject() { return HeapObject::FromAddress(area_start()); }
+
+  inline LargePage* next_page() const {
+    return static_cast<LargePage*>(next_chunk());
+  }
+
+  inline void set_next_page(LargePage* page) { set_next_chunk(page); }
+
+ private:
+  static inline LargePage* Initialize(Heap* heap, MemoryChunk* chunk);
+
+  friend class MemoryAllocator;
+};
+
+STATIC_ASSERT(sizeof(LargePage) <= MemoryChunk::kHeaderSize);
+
+// ----------------------------------------------------------------------------
+// Space is the abstract superclass for all allocation spaces.
+class Space : public Malloced {
+ public:
+  Space(Heap* heap, AllocationSpace id, Executability executable)
+      : heap_(heap), id_(id), executable_(executable) {}
+
+  virtual ~Space() {}
+
+  Heap* heap() const { return heap_; }
+
+  // Does the space need executable memory?
+  Executability executable() { return executable_; }
+
+  // Identity used in error reporting.
+  AllocationSpace identity() { return id_; }
+
+  // Returns allocated size.
+  virtual intptr_t Size() = 0;
+
+  // Returns size of objects. Can differ from the allocated size
+  // (e.g. see LargeObjectSpace).
+  virtual intptr_t SizeOfObjects() { return Size(); }
+
+  virtual int RoundSizeDownToObjectAlignment(int size) {
+    if (id_ == CODE_SPACE) {
+      return RoundDown(size, kCodeAlignment);
+    } else {
+      return RoundDown(size, kPointerSize);
+    }
+  }
+
+#ifdef DEBUG
+  virtual void Print() = 0;
+#endif
+
+ private:
+  Heap* heap_;
+  AllocationSpace id_;
+  Executability executable_;
+};
+
+
+// ----------------------------------------------------------------------------
+// All heap objects containing executable code (code objects) must be allocated
+// from a 2 GB range of memory, so that they can call each other using 32-bit
+// displacements.  This happens automatically on 32-bit platforms, where 32-bit
+// displacements cover the entire 4GB virtual address space.  On 64-bit
+// platforms, we support this using the CodeRange object, which reserves and
+// manages a range of virtual memory.
+class CodeRange {
+ public:
+  explicit CodeRange(Isolate* isolate);
+  ~CodeRange() { TearDown(); }
+
+  // Reserves a range of virtual memory, but does not commit any of it.
+  // Can only be called once, at heap initialization time.
+  // Returns false on failure.
+  bool SetUp(size_t requested_size);
+
+  // Frees the range of virtual memory, and frees the data structures used to
+  // manage it.
+  void TearDown();
+
+  bool valid() { return code_range_ != NULL; }
+  Address start() {
+    DCHECK(valid());
+    return static_cast<Address>(code_range_->address());
+  }
+  bool contains(Address address) {
+    if (!valid()) return false;
+    Address start = static_cast<Address>(code_range_->address());
+    return start <= address && address < start + code_range_->size();
+  }
+
+  // Allocates a chunk of memory from the large-object portion of
+  // the code range.  On platforms with no separate code range, should
+  // not be called.
+  MUST_USE_RESULT Address AllocateRawMemory(const size_t requested_size,
+                                            const size_t commit_size,
+                                            size_t* allocated);
+  bool CommitRawMemory(Address start, size_t length);
+  bool UncommitRawMemory(Address start, size_t length);
+  void FreeRawMemory(Address buf, size_t length);
+
+ private:
+  Isolate* isolate_;
+
+  // The reserved range of virtual memory that all code objects are put in.
+  base::VirtualMemory* code_range_;
+  // Plain old data class, just a struct plus a constructor.
+  class FreeBlock {
+   public:
+    FreeBlock(Address start_arg, size_t size_arg)
+        : start(start_arg), size(size_arg) {
+      DCHECK(IsAddressAligned(start, MemoryChunk::kAlignment));
+      DCHECK(size >= static_cast<size_t>(Page::kPageSize));
+    }
+    FreeBlock(void* start_arg, size_t size_arg)
+        : start(static_cast<Address>(start_arg)), size(size_arg) {
+      DCHECK(IsAddressAligned(start, MemoryChunk::kAlignment));
+      DCHECK(size >= static_cast<size_t>(Page::kPageSize));
+    }
+
+    Address start;
+    size_t size;
+  };
+
+  // Freed blocks of memory are added to the free list.  When the allocation
+  // list is exhausted, the free list is sorted and merged to make the new
+  // allocation list.
+  List<FreeBlock> free_list_;
+  // Memory is allocated from the free blocks on the allocation list.
+  // The block at current_allocation_block_index_ is the current block.
+  List<FreeBlock> allocation_list_;
+  int current_allocation_block_index_;
+
+  // Finds a block on the allocation list that contains at least the
+  // requested amount of memory.  If none is found, sorts and merges
+  // the existing free memory blocks, and searches again.
+  // If none can be found, returns false.
+  bool GetNextAllocationBlock(size_t requested);
+  // Compares the start addresses of two free blocks.
+  static int CompareFreeBlockAddress(const FreeBlock* left,
+                                     const FreeBlock* right);
+
+  DISALLOW_COPY_AND_ASSIGN(CodeRange);
+};
+
+
+class SkipList {
+ public:
+  SkipList() { Clear(); }
+
+  void Clear() {
+    for (int idx = 0; idx < kSize; idx++) {
+      starts_[idx] = reinterpret_cast<Address>(-1);
+    }
+  }
+
+  Address StartFor(Address addr) { return starts_[RegionNumber(addr)]; }
+
+  void AddObject(Address addr, int size) {
+    int start_region = RegionNumber(addr);
+    int end_region = RegionNumber(addr + size - kPointerSize);
+    for (int idx = start_region; idx <= end_region; idx++) {
+      if (starts_[idx] > addr) starts_[idx] = addr;
+    }
+  }
+
+  static inline int RegionNumber(Address addr) {
+    return (OffsetFrom(addr) & Page::kPageAlignmentMask) >> kRegionSizeLog2;
+  }
+
+  static void Update(Address addr, int size) {
+    Page* page = Page::FromAddress(addr);
+    SkipList* list = page->skip_list();
+    if (list == NULL) {
+      list = new SkipList();
+      page->set_skip_list(list);
+    }
+
+    list->AddObject(addr, size);
+  }
+
+ private:
+  static const int kRegionSizeLog2 = 13;
+  static const int kRegionSize = 1 << kRegionSizeLog2;
+  static const int kSize = Page::kPageSize / kRegionSize;
+
+  STATIC_ASSERT(Page::kPageSize % kRegionSize == 0);
+
+  Address starts_[kSize];
+};
+
+
+// ----------------------------------------------------------------------------
+// A space acquires chunks of memory from the operating system. The memory
+// allocator allocated and deallocates pages for the paged heap spaces and large
+// pages for large object space.
+//
+// Each space has to manage it's own pages.
+//
+class MemoryAllocator {
+ public:
+  explicit MemoryAllocator(Isolate* isolate);
+
+  // Initializes its internal bookkeeping structures.
+  // Max capacity of the total space and executable memory limit.
+  bool SetUp(intptr_t max_capacity, intptr_t capacity_executable);
+
+  void TearDown();
+
+  Page* AllocatePage(intptr_t size, PagedSpace* owner,
+                     Executability executable);
+
+  LargePage* AllocateLargePage(intptr_t object_size, Space* owner,
+                               Executability executable);
+
+  void Free(MemoryChunk* chunk);
+
+  // Returns the maximum available bytes of heaps.
+  intptr_t Available() { return capacity_ < size_ ? 0 : capacity_ - size_; }
+
+  // Returns allocated spaces in bytes.
+  intptr_t Size() { return size_; }
+
+  // Returns the maximum available executable bytes of heaps.
+  intptr_t AvailableExecutable() {
+    if (capacity_executable_ < size_executable_) return 0;
+    return capacity_executable_ - size_executable_;
+  }
+
+  // Returns allocated executable spaces in bytes.
+  intptr_t SizeExecutable() { return size_executable_; }
+
+  // Returns maximum available bytes that the old space can have.
+  intptr_t MaxAvailable() {
+    return (Available() / Page::kPageSize) * Page::kMaxRegularHeapObjectSize;
+  }
+
+  // Returns an indication of whether a pointer is in a space that has
+  // been allocated by this MemoryAllocator.
+  V8_INLINE bool IsOutsideAllocatedSpace(const void* address) const {
+    return address < lowest_ever_allocated_ ||
+           address >= highest_ever_allocated_;
+  }
+
+#ifdef DEBUG
+  // Reports statistic info of the space.
+  void ReportStatistics();
+#endif
+
+  // Returns a MemoryChunk in which the memory region from commit_area_size to
+  // reserve_area_size of the chunk area is reserved but not committed, it
+  // could be committed later by calling MemoryChunk::CommitArea.
+  MemoryChunk* AllocateChunk(intptr_t reserve_area_size,
+                             intptr_t commit_area_size,
+                             Executability executable, Space* space);
+
+  Address ReserveAlignedMemory(size_t requested, size_t alignment,
+                               base::VirtualMemory* controller);
+  Address AllocateAlignedMemory(size_t reserve_size, size_t commit_size,
+                                size_t alignment, Executability executable,
+                                base::VirtualMemory* controller);
+
+  bool CommitMemory(Address addr, size_t size, Executability executable);
+
+  void FreeMemory(base::VirtualMemory* reservation, Executability executable);
+  void FreeMemory(Address addr, size_t size, Executability executable);
+
+  // Commit a contiguous block of memory from the initial chunk.  Assumes that
+  // the address is not NULL, the size is greater than zero, and that the
+  // block is contained in the initial chunk.  Returns true if it succeeded
+  // and false otherwise.
+  bool CommitBlock(Address start, size_t size, Executability executable);
+
+  // Uncommit a contiguous block of memory [start..(start+size)[.
+  // start is not NULL, the size is greater than zero, and the
+  // block is contained in the initial chunk.  Returns true if it succeeded
+  // and false otherwise.
+  bool UncommitBlock(Address start, size_t size);
+
+  // Zaps a contiguous block of memory [start..(start+size)[ thus
+  // filling it up with a recognizable non-NULL bit pattern.
+  void ZapBlock(Address start, size_t size);
+
+  void PerformAllocationCallback(ObjectSpace space, AllocationAction action,
+                                 size_t size);
+
+  void AddMemoryAllocationCallback(MemoryAllocationCallback callback,
+                                   ObjectSpace space, AllocationAction action);
+
+  void RemoveMemoryAllocationCallback(MemoryAllocationCallback callback);
+
+  bool MemoryAllocationCallbackRegistered(MemoryAllocationCallback callback);
+
+  static int CodePageGuardStartOffset();
+
+  static int CodePageGuardSize();
+
+  static int CodePageAreaStartOffset();
+
+  static int CodePageAreaEndOffset();
+
+  static int CodePageAreaSize() {
+    return CodePageAreaEndOffset() - CodePageAreaStartOffset();
+  }
+
+  MUST_USE_RESULT bool CommitExecutableMemory(base::VirtualMemory* vm,
+                                              Address start, size_t commit_size,
+                                              size_t reserved_size);
+
+ private:
+  Isolate* isolate_;
+
+  // Maximum space size in bytes.
+  size_t capacity_;
+  // Maximum subset of capacity_ that can be executable
+  size_t capacity_executable_;
+
+  // Allocated space size in bytes.
+  size_t size_;
+  // Allocated executable space size in bytes.
+  size_t size_executable_;
+
+  // We keep the lowest and highest addresses allocated as a quick way
+  // of determining that pointers are outside the heap. The estimate is
+  // conservative, i.e. not all addrsses in 'allocated' space are allocated
+  // to our heap. The range is [lowest, highest[, inclusive on the low end
+  // and exclusive on the high end.
+  void* lowest_ever_allocated_;
+  void* highest_ever_allocated_;
+
+  struct MemoryAllocationCallbackRegistration {
+    MemoryAllocationCallbackRegistration(MemoryAllocationCallback callback,
+                                         ObjectSpace space,
+                                         AllocationAction action)
+        : callback(callback), space(space), action(action) {}
+    MemoryAllocationCallback callback;
+    ObjectSpace space;
+    AllocationAction action;
+  };
+
+  // A List of callback that are triggered when memory is allocated or free'd
+  List<MemoryAllocationCallbackRegistration> memory_allocation_callbacks_;
+
+  // Initializes pages in a chunk. Returns the first page address.
+  // This function and GetChunkId() are provided for the mark-compact
+  // collector to rebuild page headers in the from space, which is
+  // used as a marking stack and its page headers are destroyed.
+  Page* InitializePagesInChunk(int chunk_id, int pages_in_chunk,
+                               PagedSpace* owner);
+
+  void UpdateAllocatedSpaceLimits(void* low, void* high) {
+    lowest_ever_allocated_ = Min(lowest_ever_allocated_, low);
+    highest_ever_allocated_ = Max(highest_ever_allocated_, high);
+  }
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(MemoryAllocator);
+};
+
+
+// -----------------------------------------------------------------------------
+// Interface for heap object iterator to be implemented by all object space
+// object iterators.
+//
+// NOTE: The space specific object iterators also implements the own next()
+//       method which is used to avoid using virtual functions
+//       iterating a specific space.
+
+class ObjectIterator : public Malloced {
+ public:
+  virtual ~ObjectIterator() {}
+
+  virtual HeapObject* next_object() = 0;
+};
+
+
+// -----------------------------------------------------------------------------
+// Heap object iterator in new/old/map spaces.
+//
+// A HeapObjectIterator iterates objects from the bottom of the given space
+// to its top or from the bottom of the given page to its top.
+//
+// If objects are allocated in the page during iteration the iterator may
+// or may not iterate over those objects.  The caller must create a new
+// iterator in order to be sure to visit these new objects.
+class HeapObjectIterator : public ObjectIterator {
+ public:
+  // Creates a new object iterator in a given space.
+  // If the size function is not given, the iterator calls the default
+  // Object::Size().
+  explicit HeapObjectIterator(PagedSpace* space);
+  HeapObjectIterator(PagedSpace* space, HeapObjectCallback size_func);
+  HeapObjectIterator(Page* page, HeapObjectCallback size_func);
+
+  // Advance to the next object, skipping free spaces and other fillers and
+  // skipping the special garbage section of which there is one per space.
+  // Returns NULL when the iteration has ended.
+  inline HeapObject* Next() {
+    do {
+      HeapObject* next_obj = FromCurrentPage();
+      if (next_obj != NULL) return next_obj;
+    } while (AdvanceToNextPage());
+    return NULL;
+  }
+
+  virtual HeapObject* next_object() { return Next(); }
+
+ private:
+  enum PageMode { kOnePageOnly, kAllPagesInSpace };
+
+  Address cur_addr_;              // Current iteration point.
+  Address cur_end_;               // End iteration point.
+  HeapObjectCallback size_func_;  // Size function or NULL.
+  PagedSpace* space_;
+  PageMode page_mode_;
+
+  // Fast (inlined) path of next().
+  inline HeapObject* FromCurrentPage();
+
+  // Slow path of next(), goes into the next page.  Returns false if the
+  // iteration has ended.
+  bool AdvanceToNextPage();
+
+  // Initializes fields.
+  inline void Initialize(PagedSpace* owner, Address start, Address end,
+                         PageMode mode, HeapObjectCallback size_func);
+};
+
+
+// -----------------------------------------------------------------------------
+// A PageIterator iterates the pages in a paged space.
+
+class PageIterator BASE_EMBEDDED {
+ public:
+  explicit inline PageIterator(PagedSpace* space);
+
+  inline bool has_next();
+  inline Page* next();
+
+ private:
+  PagedSpace* space_;
+  Page* prev_page_;  // Previous page returned.
+  // Next page that will be returned.  Cached here so that we can use this
+  // iterator for operations that deallocate pages.
+  Page* next_page_;
+};
+
+
+// -----------------------------------------------------------------------------
+// A space has a circular list of pages. The next page can be accessed via
+// Page::next_page() call.
+
+// An abstraction of allocation and relocation pointers in a page-structured
+// space.
+class AllocationInfo {
+ public:
+  AllocationInfo() : top_(NULL), limit_(NULL) {}
+
+  INLINE(void set_top(Address top)) {
+    SLOW_DCHECK(top == NULL ||
+                (reinterpret_cast<intptr_t>(top) & HeapObjectTagMask()) == 0);
+    top_ = top;
+  }
+
+  INLINE(Address top()) const {
+    SLOW_DCHECK(top_ == NULL ||
+                (reinterpret_cast<intptr_t>(top_) & HeapObjectTagMask()) == 0);
+    return top_;
+  }
+
+  Address* top_address() { return &top_; }
+
+  INLINE(void set_limit(Address limit)) {
+    SLOW_DCHECK(limit == NULL ||
+                (reinterpret_cast<intptr_t>(limit) & HeapObjectTagMask()) == 0);
+    limit_ = limit;
+  }
+
+  INLINE(Address limit()) const {
+    SLOW_DCHECK(limit_ == NULL ||
+                (reinterpret_cast<intptr_t>(limit_) & HeapObjectTagMask()) ==
+                    0);
+    return limit_;
+  }
+
+  Address* limit_address() { return &limit_; }
+
+#ifdef DEBUG
+  bool VerifyPagedAllocation() {
+    return (Page::FromAllocationTop(top_) == Page::FromAllocationTop(limit_)) &&
+           (top_ <= limit_);
+  }
+#endif
+
+ private:
+  // Current allocation top.
+  Address top_;
+  // Current allocation limit.
+  Address limit_;
+};
+
+
+// An abstraction of the accounting statistics of a page-structured space.
+// The 'capacity' of a space is the number of object-area bytes (i.e., not
+// including page bookkeeping structures) currently in the space. The 'size'
+// of a space is the number of allocated bytes, the 'waste' in the space is
+// the number of bytes that are not allocated and not available to
+// allocation without reorganizing the space via a GC (e.g. small blocks due
+// to internal fragmentation, top of page areas in map space), and the bytes
+// 'available' is the number of unallocated bytes that are not waste.  The
+// capacity is the sum of size, waste, and available.
+//
+// The stats are only set by functions that ensure they stay balanced. These
+// functions increase or decrease one of the non-capacity stats in
+// conjunction with capacity, or else they always balance increases and
+// decreases to the non-capacity stats.
+class AllocationStats BASE_EMBEDDED {
+ public:
+  AllocationStats() { Clear(); }
+
+  // Zero out all the allocation statistics (i.e., no capacity).
+  void Clear() {
+    capacity_ = 0;
+    max_capacity_ = 0;
+    size_ = 0;
+    waste_ = 0;
+  }
+
+  void ClearSizeWaste() {
+    size_ = capacity_;
+    waste_ = 0;
+  }
+
+  // Reset the allocation statistics (i.e., available = capacity with no
+  // wasted or allocated bytes).
+  void Reset() {
+    size_ = 0;
+    waste_ = 0;
+  }
+
+  // Accessors for the allocation statistics.
+  intptr_t Capacity() { return capacity_; }
+  intptr_t MaxCapacity() { return max_capacity_; }
+  intptr_t Size() { return size_; }
+  intptr_t Waste() { return waste_; }
+
+  // Grow the space by adding available bytes.  They are initially marked as
+  // being in use (part of the size), but will normally be immediately freed,
+  // putting them on the free list and removing them from size_.
+  void ExpandSpace(int size_in_bytes) {
+    capacity_ += size_in_bytes;
+    size_ += size_in_bytes;
+    if (capacity_ > max_capacity_) {
+      max_capacity_ = capacity_;
+    }
+    DCHECK(size_ >= 0);
+  }
+
+  // Shrink the space by removing available bytes.  Since shrinking is done
+  // during sweeping, bytes have been marked as being in use (part of the size)
+  // and are hereby freed.
+  void ShrinkSpace(int size_in_bytes) {
+    capacity_ -= size_in_bytes;
+    size_ -= size_in_bytes;
+    DCHECK(size_ >= 0);
+  }
+
+  // Allocate from available bytes (available -> size).
+  void AllocateBytes(intptr_t size_in_bytes) {
+    size_ += size_in_bytes;
+    DCHECK(size_ >= 0);
+  }
+
+  // Free allocated bytes, making them available (size -> available).
+  void DeallocateBytes(intptr_t size_in_bytes) {
+    size_ -= size_in_bytes;
+    DCHECK(size_ >= 0);
+  }
+
+  // Waste free bytes (available -> waste).
+  void WasteBytes(int size_in_bytes) {
+    DCHECK(size_in_bytes >= 0);
+    waste_ += size_in_bytes;
+  }
+
+ private:
+  intptr_t capacity_;
+  intptr_t max_capacity_;
+  intptr_t size_;
+  intptr_t waste_;
+};
+
+
+// -----------------------------------------------------------------------------
+// Free lists for old object spaces
+//
+// Free-list nodes are free blocks in the heap.  They look like heap objects
+// (free-list node pointers have the heap object tag, and they have a map like
+// a heap object).  They have a size and a next pointer.  The next pointer is
+// the raw address of the next free list node (or NULL).
+class FreeListNode : public HeapObject {
+ public:
+  // Obtain a free-list node from a raw address.  This is not a cast because
+  // it does not check nor require that the first word at the address is a map
+  // pointer.
+  static FreeListNode* FromAddress(Address address) {
+    return reinterpret_cast<FreeListNode*>(HeapObject::FromAddress(address));
+  }
+
+  static inline bool IsFreeListNode(HeapObject* object);
+
+  // Set the size in bytes, which can be read with HeapObject::Size().  This
+  // function also writes a map to the first word of the block so that it
+  // looks like a heap object to the garbage collector and heap iteration
+  // functions.
+  void set_size(Heap* heap, int size_in_bytes);
+
+  // Accessors for the next field.
+  inline FreeListNode* next();
+  inline FreeListNode** next_address();
+  inline void set_next(FreeListNode* next);
+
+  inline void Zap();
+
+  static inline FreeListNode* cast(Object* object) {
+    return reinterpret_cast<FreeListNode*>(object);
+  }
+
+ private:
+  static const int kNextOffset = POINTER_SIZE_ALIGN(FreeSpace::kHeaderSize);
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(FreeListNode);
+};
+
+
+// The free list category holds a pointer to the top element and a pointer to
+// the end element of the linked list of free memory blocks.
+class FreeListCategory {
+ public:
+  FreeListCategory() : top_(0), end_(NULL), available_(0) {}
+
+  intptr_t Concatenate(FreeListCategory* category);
+
+  void Reset();
+
+  void Free(FreeListNode* node, int size_in_bytes);
+
+  FreeListNode* PickNodeFromList(int* node_size);
+  FreeListNode* PickNodeFromList(int size_in_bytes, int* node_size);
+
+  intptr_t EvictFreeListItemsInList(Page* p);
+  bool ContainsPageFreeListItemsInList(Page* p);
+
+  void RepairFreeList(Heap* heap);
+
+  FreeListNode* top() const {
+    return reinterpret_cast<FreeListNode*>(base::NoBarrier_Load(&top_));
+  }
+
+  void set_top(FreeListNode* top) {
+    base::NoBarrier_Store(&top_, reinterpret_cast<base::AtomicWord>(top));
+  }
+
+  FreeListNode** GetEndAddress() { return &end_; }
+  FreeListNode* end() const { return end_; }
+  void set_end(FreeListNode* end) { end_ = end; }
+
+  int* GetAvailableAddress() { return &available_; }
+  int available() const { return available_; }
+  void set_available(int available) { available_ = available; }
+
+  base::Mutex* mutex() { return &mutex_; }
+
+  bool IsEmpty() { return top() == 0; }
+
+#ifdef DEBUG
+  intptr_t SumFreeList();
+  int FreeListLength();
+#endif
+
+ private:
+  // top_ points to the top FreeListNode* in the free list category.
+  base::AtomicWord top_;
+  FreeListNode* end_;
+  base::Mutex mutex_;
+
+  // Total available bytes in all blocks of this free list category.
+  int available_;
+};
+
+
+// The free list for the old space.  The free list is organized in such a way
+// as to encourage objects allocated around the same time to be near each
+// other.  The normal way to allocate is intended to be by bumping a 'top'
+// pointer until it hits a 'limit' pointer.  When the limit is hit we need to
+// find a new space to allocate from.  This is done with the free list, which
+// is divided up into rough categories to cut down on waste.  Having finer
+// categories would scatter allocation more.
+
+// The old space free list is organized in categories.
+// 1-31 words:  Such small free areas are discarded for efficiency reasons.
+//     They can be reclaimed by the compactor.  However the distance between top
+//     and limit may be this small.
+// 32-255 words: There is a list of spaces this large.  It is used for top and
+//     limit when the object we need to allocate is 1-31 words in size.  These
+//     spaces are called small.
+// 256-2047 words: There is a list of spaces this large.  It is used for top and
+//     limit when the object we need to allocate is 32-255 words in size.  These
+//     spaces are called medium.
+// 1048-16383 words: There is a list of spaces this large.  It is used for top
+//     and limit when the object we need to allocate is 256-2047 words in size.
+//     These spaces are call large.
+// At least 16384 words.  This list is for objects of 2048 words or larger.
+//     Empty pages are added to this list.  These spaces are called huge.
+class FreeList {
+ public:
+  explicit FreeList(PagedSpace* owner);
+
+  intptr_t Concatenate(FreeList* free_list);
+
+  // Clear the free list.
+  void Reset();
+
+  // Return the number of bytes available on the free list.
+  intptr_t available() {
+    return small_list_.available() + medium_list_.available() +
+           large_list_.available() + huge_list_.available();
+  }
+
+  // Place a node on the free list.  The block of size 'size_in_bytes'
+  // starting at 'start' is placed on the free list.  The return value is the
+  // number of bytes that have been lost due to internal fragmentation by
+  // freeing the block.  Bookkeeping information will be written to the block,
+  // i.e., its contents will be destroyed.  The start address should be word
+  // aligned, and the size should be a non-zero multiple of the word size.
+  int Free(Address start, int size_in_bytes);
+
+  // This method returns how much memory can be allocated after freeing
+  // maximum_freed memory.
+  static inline int GuaranteedAllocatable(int maximum_freed) {
+    if (maximum_freed < kSmallListMin) {
+      return 0;
+    } else if (maximum_freed <= kSmallListMax) {
+      return kSmallAllocationMax;
+    } else if (maximum_freed <= kMediumListMax) {
+      return kMediumAllocationMax;
+    } else if (maximum_freed <= kLargeListMax) {
+      return kLargeAllocationMax;
+    }
+    return maximum_freed;
+  }
+
+  // Allocate a block of size 'size_in_bytes' from the free list.  The block
+  // is unitialized.  A failure is returned if no block is available.  The
+  // number of bytes lost to fragmentation is returned in the output parameter
+  // 'wasted_bytes'.  The size should be a non-zero multiple of the word size.
+  MUST_USE_RESULT HeapObject* Allocate(int size_in_bytes);
+
+  bool IsEmpty() {
+    return small_list_.IsEmpty() && medium_list_.IsEmpty() &&
+           large_list_.IsEmpty() && huge_list_.IsEmpty();
+  }
+
+#ifdef DEBUG
+  void Zap();
+  intptr_t SumFreeLists();
+  bool IsVeryLong();
+#endif
+
+  // Used after booting the VM.
+  void RepairLists(Heap* heap);
+
+  intptr_t EvictFreeListItems(Page* p);
+  bool ContainsPageFreeListItems(Page* p);
+
+  FreeListCategory* small_list() { return &small_list_; }
+  FreeListCategory* medium_list() { return &medium_list_; }
+  FreeListCategory* large_list() { return &large_list_; }
+  FreeListCategory* huge_list() { return &huge_list_; }
+
+ private:
+  // The size range of blocks, in bytes.
+  static const int kMinBlockSize = 3 * kPointerSize;
+  static const int kMaxBlockSize = Page::kMaxRegularHeapObjectSize;
+
+  FreeListNode* FindNodeFor(int size_in_bytes, int* node_size);
+
+  PagedSpace* owner_;
+  Heap* heap_;
+
+  static const int kSmallListMin = 0x20 * kPointerSize;
+  static const int kSmallListMax = 0xff * kPointerSize;
+  static const int kMediumListMax = 0x7ff * kPointerSize;
+  static const int kLargeListMax = 0x3fff * kPointerSize;
+  static const int kSmallAllocationMax = kSmallListMin - kPointerSize;
+  static const int kMediumAllocationMax = kSmallListMax;
+  static const int kLargeAllocationMax = kMediumListMax;
+  FreeListCategory small_list_;
+  FreeListCategory medium_list_;
+  FreeListCategory large_list_;
+  FreeListCategory huge_list_;
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(FreeList);
+};
+
+
+class AllocationResult {
+ public:
+  // Implicit constructor from Object*.
+  AllocationResult(Object* object)  // NOLINT
+      : object_(object),
+        retry_space_(INVALID_SPACE) {}
+
+  AllocationResult() : object_(NULL), retry_space_(INVALID_SPACE) {}
+
+  static inline AllocationResult Retry(AllocationSpace space = NEW_SPACE) {
+    return AllocationResult(space);
+  }
+
+  inline bool IsRetry() { return retry_space_ != INVALID_SPACE; }
+
+  template <typename T>
+  bool To(T** obj) {
+    if (IsRetry()) return false;
+    *obj = T::cast(object_);
+    return true;
+  }
+
+  Object* ToObjectChecked() {
+    CHECK(!IsRetry());
+    return object_;
+  }
+
+  AllocationSpace RetrySpace() {
+    DCHECK(IsRetry());
+    return retry_space_;
+  }
+
+ private:
+  explicit AllocationResult(AllocationSpace space)
+      : object_(NULL), retry_space_(space) {}
+
+  Object* object_;
+  AllocationSpace retry_space_;
+};
+
+
+class PagedSpace : public Space {
+ public:
+  // Creates a space with a maximum capacity, and an id.
+  PagedSpace(Heap* heap, intptr_t max_capacity, AllocationSpace id,
+             Executability executable);
+
+  virtual ~PagedSpace() {}
+
+  // Set up the space using the given address range of virtual memory (from
+  // the memory allocator's initial chunk) if possible.  If the block of
+  // addresses is not big enough to contain a single page-aligned page, a
+  // fresh chunk will be allocated.
+  bool SetUp();
+
+  // Returns true if the space has been successfully set up and not
+  // subsequently torn down.
+  bool HasBeenSetUp();
+
+  // Cleans up the space, frees all pages in this space except those belonging
+  // to the initial chunk, uncommits addresses in the initial chunk.
+  void TearDown();
+
+  // Checks whether an object/address is in this space.
+  inline bool Contains(Address a);
+  bool Contains(HeapObject* o) { return Contains(o->address()); }
+
+  // Given an address occupied by a live object, return that object if it is
+  // in this space, or a Smi if it is not.  The implementation iterates over
+  // objects in the page containing the address, the cost is linear in the
+  // number of objects in the page.  It may be slow.
+  Object* FindObject(Address addr);
+
+  // During boot the free_space_map is created, and afterwards we may need
+  // to write it into the free list nodes that were already created.
+  void RepairFreeListsAfterBoot();
+
+  // Prepares for a mark-compact GC.
+  void PrepareForMarkCompact();
+
+  // Current capacity without growing (Size() + Available()).
+  intptr_t Capacity() { return accounting_stats_.Capacity(); }
+
+  // Total amount of memory committed for this space.  For paged
+  // spaces this equals the capacity.
+  intptr_t CommittedMemory() { return Capacity(); }
+
+  // The maximum amount of memory ever committed for this space.
+  intptr_t MaximumCommittedMemory() { return accounting_stats_.MaxCapacity(); }
+
+  // Approximate amount of physical memory committed for this space.
+  size_t CommittedPhysicalMemory();
+
+  struct SizeStats {
+    intptr_t Total() {
+      return small_size_ + medium_size_ + large_size_ + huge_size_;
+    }
+
+    intptr_t small_size_;
+    intptr_t medium_size_;
+    intptr_t large_size_;
+    intptr_t huge_size_;
+  };
+
+  void ObtainFreeListStatistics(Page* p, SizeStats* sizes);
+  void ResetFreeListStatistics();
+
+  // Sets the capacity, the available space and the wasted space to zero.
+  // The stats are rebuilt during sweeping by adding each page to the
+  // capacity and the size when it is encountered.  As free spaces are
+  // discovered during the sweeping they are subtracted from the size and added
+  // to the available and wasted totals.
+  void ClearStats() {
+    accounting_stats_.ClearSizeWaste();
+    ResetFreeListStatistics();
+  }
+
+  // Increases the number of available bytes of that space.
+  void AddToAccountingStats(intptr_t bytes) {
+    accounting_stats_.DeallocateBytes(bytes);
+  }
+
+  // Available bytes without growing.  These are the bytes on the free list.
+  // The bytes in the linear allocation area are not included in this total
+  // because updating the stats would slow down allocation.  New pages are
+  // immediately added to the free list so they show up here.
+  intptr_t Available() { return free_list_.available(); }
+
+  // Allocated bytes in this space.  Garbage bytes that were not found due to
+  // concurrent sweeping are counted as being allocated!  The bytes in the
+  // current linear allocation area (between top and limit) are also counted
+  // here.
+  virtual intptr_t Size() { return accounting_stats_.Size(); }
+
+  // As size, but the bytes in lazily swept pages are estimated and the bytes
+  // in the current linear allocation area are not included.
+  virtual intptr_t SizeOfObjects();
+
+  // Wasted bytes in this space.  These are just the bytes that were thrown away
+  // due to being too small to use for allocation.  They do not include the
+  // free bytes that were not found at all due to lazy sweeping.
+  virtual intptr_t Waste() { return accounting_stats_.Waste(); }
+
+  // Returns the allocation pointer in this space.
+  Address top() { return allocation_info_.top(); }
+  Address limit() { return allocation_info_.limit(); }
+
+  // The allocation top address.
+  Address* allocation_top_address() { return allocation_info_.top_address(); }
+
+  // The allocation limit address.
+  Address* allocation_limit_address() {
+    return allocation_info_.limit_address();
+  }
+
+  // Allocate the requested number of bytes in the space if possible, return a
+  // failure object if not.
+  MUST_USE_RESULT inline AllocationResult AllocateRaw(int size_in_bytes);
+
+  // Give a block of memory to the space's free list.  It might be added to
+  // the free list or accounted as waste.
+  // If add_to_freelist is false then just accounting stats are updated and
+  // no attempt to add area to free list is made.
+  int Free(Address start, int size_in_bytes) {
+    int wasted = free_list_.Free(start, size_in_bytes);
+    accounting_stats_.DeallocateBytes(size_in_bytes);
+    accounting_stats_.WasteBytes(wasted);
+    return size_in_bytes - wasted;
+  }
+
+  void ResetFreeList() { free_list_.Reset(); }
+
+  // Set space allocation info.
+  void SetTopAndLimit(Address top, Address limit) {
+    DCHECK(top == limit ||
+           Page::FromAddress(top) == Page::FromAddress(limit - 1));
+    MemoryChunk::UpdateHighWaterMark(allocation_info_.top());
+    allocation_info_.set_top(top);
+    allocation_info_.set_limit(limit);
+  }
+
+  // Empty space allocation info, returning unused area to free list.
+  void EmptyAllocationInfo() {
+    // Mark the old linear allocation area with a free space map so it can be
+    // skipped when scanning the heap.
+    int old_linear_size = static_cast<int>(limit() - top());
+    Free(top(), old_linear_size);
+    SetTopAndLimit(NULL, NULL);
+  }
+
+  void Allocate(int bytes) { accounting_stats_.AllocateBytes(bytes); }
+
+  void IncreaseCapacity(int size);
+
+  // Releases an unused page and shrinks the space.
+  void ReleasePage(Page* page);
+
+  // The dummy page that anchors the linked list of pages.
+  Page* anchor() { return &anchor_; }
+
+#ifdef VERIFY_HEAP
+  // Verify integrity of this space.
+  virtual void Verify(ObjectVisitor* visitor);
+
+  // Overridden by subclasses to verify space-specific object
+  // properties (e.g., only maps or free-list nodes are in map space).
+  virtual void VerifyObject(HeapObject* obj) {}
+#endif
+
+#ifdef DEBUG
+  // Print meta info and objects in this space.
+  virtual void Print();
+
+  // Reports statistics for the space
+  void ReportStatistics();
+
+  // Report code object related statistics
+  void CollectCodeStatistics();
+  static void ReportCodeStatistics(Isolate* isolate);
+  static void ResetCodeStatistics(Isolate* isolate);
+#endif
+
+  // Evacuation candidates are swept by evacuator.  Needs to return a valid
+  // result before _and_ after evacuation has finished.
+  static bool ShouldBeSweptBySweeperThreads(Page* p) {
+    return !p->IsEvacuationCandidate() &&
+           !p->IsFlagSet(Page::RESCAN_ON_EVACUATION) && !p->WasSwept();
+  }
+
+  void IncrementUnsweptFreeBytes(intptr_t by) { unswept_free_bytes_ += by; }
+
+  void IncreaseUnsweptFreeBytes(Page* p) {
+    DCHECK(ShouldBeSweptBySweeperThreads(p));
+    unswept_free_bytes_ += (p->area_size() - p->LiveBytes());
+  }
+
+  void DecrementUnsweptFreeBytes(intptr_t by) { unswept_free_bytes_ -= by; }
+
+  void DecreaseUnsweptFreeBytes(Page* p) {
+    DCHECK(ShouldBeSweptBySweeperThreads(p));
+    unswept_free_bytes_ -= (p->area_size() - p->LiveBytes());
+  }
+
+  void ResetUnsweptFreeBytes() { unswept_free_bytes_ = 0; }
+
+  // This function tries to steal size_in_bytes memory from the sweeper threads
+  // free-lists. If it does not succeed stealing enough memory, it will wait
+  // for the sweeper threads to finish sweeping.
+  // It returns true when sweeping is completed and false otherwise.
+  bool EnsureSweeperProgress(intptr_t size_in_bytes);
+
+  void set_end_of_unswept_pages(Page* page) { end_of_unswept_pages_ = page; }
+
+  Page* end_of_unswept_pages() { return end_of_unswept_pages_; }
+
+  Page* FirstPage() { return anchor_.next_page(); }
+  Page* LastPage() { return anchor_.prev_page(); }
+
+  void EvictEvacuationCandidatesFromFreeLists();
+
+  bool CanExpand();
+
+  // Returns the number of total pages in this space.
+  int CountTotalPages();
+
+  // Return size of allocatable area on a page in this space.
+  inline int AreaSize() { return area_size_; }
+
+  void CreateEmergencyMemory();
+  void FreeEmergencyMemory();
+  void UseEmergencyMemory();
+
+  bool HasEmergencyMemory() { return emergency_memory_ != NULL; }
+
+ protected:
+  FreeList* free_list() { return &free_list_; }
+
+  int area_size_;
+
+  // Maximum capacity of this space.
+  intptr_t max_capacity_;
+
+  intptr_t SizeOfFirstPage();
+
+  // Accounting information for this space.
+  AllocationStats accounting_stats_;
+
+  // The dummy page that anchors the double linked list of pages.
+  Page anchor_;
+
+  // The space's free list.
+  FreeList free_list_;
+
+  // Normal allocation information.
+  AllocationInfo allocation_info_;
+
+  // The number of free bytes which could be reclaimed by advancing the
+  // concurrent sweeper threads.
+  intptr_t unswept_free_bytes_;
+
+  // The sweeper threads iterate over the list of pointer and data space pages
+  // and sweep these pages concurrently. They will stop sweeping after the
+  // end_of_unswept_pages_ page.
+  Page* end_of_unswept_pages_;
+
+  // Emergency memory is the memory of a full page for a given space, allocated
+  // conservatively before evacuating a page. If compaction fails due to out
+  // of memory error the emergency memory can be used to complete compaction.
+  // If not used, the emergency memory is released after compaction.
+  MemoryChunk* emergency_memory_;
+
+  // Expands the space by allocating a fixed number of pages. Returns false if
+  // it cannot allocate requested number of pages from OS, or if the hard heap
+  // size limit has been hit.
+  bool Expand();
+
+  // Generic fast case allocation function that tries linear allocation at the
+  // address denoted by top in allocation_info_.
+  inline HeapObject* AllocateLinearly(int size_in_bytes);
+
+  // If sweeping is still in progress try to sweep unswept pages. If that is
+  // not successful, wait for the sweeper threads and re-try free-list
+  // allocation.
+  MUST_USE_RESULT HeapObject* WaitForSweeperThreadsAndRetryAllocation(
+      int size_in_bytes);
+
+  // Slow path of AllocateRaw.  This function is space-dependent.
+  MUST_USE_RESULT HeapObject* SlowAllocateRaw(int size_in_bytes);
+
+  friend class PageIterator;
+  friend class MarkCompactCollector;
+};
+
+
+class NumberAndSizeInfo BASE_EMBEDDED {
+ public:
+  NumberAndSizeInfo() : number_(0), bytes_(0) {}
+
+  int number() const { return number_; }
+  void increment_number(int num) { number_ += num; }
+
+  int bytes() const { return bytes_; }
+  void increment_bytes(int size) { bytes_ += size; }
+
+  void clear() {
+    number_ = 0;
+    bytes_ = 0;
+  }
+
+ private:
+  int number_;
+  int bytes_;
+};
+
+
+// HistogramInfo class for recording a single "bar" of a histogram.  This
+// class is used for collecting statistics to print to the log file.
+class HistogramInfo : public NumberAndSizeInfo {
+ public:
+  HistogramInfo() : NumberAndSizeInfo() {}
+
+  const char* name() { return name_; }
+  void set_name(const char* name) { name_ = name; }
+
+ private:
+  const char* name_;
+};
+
+
+enum SemiSpaceId { kFromSpace = 0, kToSpace = 1 };
+
+
+class SemiSpace;
+
+
+class NewSpacePage : public MemoryChunk {
+ public:
+  // GC related flags copied from from-space to to-space when
+  // flipping semispaces.
+  static const intptr_t kCopyOnFlipFlagsMask =
+      (1 << MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING) |
+      (1 << MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING) |
+      (1 << MemoryChunk::SCAN_ON_SCAVENGE);
+
+  static const int kAreaSize = Page::kMaxRegularHeapObjectSize;
+
+  inline NewSpacePage* next_page() const {
+    return static_cast<NewSpacePage*>(next_chunk());
+  }
+
+  inline void set_next_page(NewSpacePage* page) { set_next_chunk(page); }
+
+  inline NewSpacePage* prev_page() const {
+    return static_cast<NewSpacePage*>(prev_chunk());
+  }
+
+  inline void set_prev_page(NewSpacePage* page) { set_prev_chunk(page); }
+
+  SemiSpace* semi_space() { return reinterpret_cast<SemiSpace*>(owner()); }
+
+  bool is_anchor() { return !this->InNewSpace(); }
+
+  static bool IsAtStart(Address addr) {
+    return (reinterpret_cast<intptr_t>(addr) & Page::kPageAlignmentMask) ==
+           kObjectStartOffset;
+  }
+
+  static bool IsAtEnd(Address addr) {
+    return (reinterpret_cast<intptr_t>(addr) & Page::kPageAlignmentMask) == 0;
+  }
+
+  Address address() { return reinterpret_cast<Address>(this); }
+
+  // Finds the NewSpacePage containing the given address.
+  static inline NewSpacePage* FromAddress(Address address_in_page) {
+    Address page_start =
+        reinterpret_cast<Address>(reinterpret_cast<uintptr_t>(address_in_page) &
+                                  ~Page::kPageAlignmentMask);
+    NewSpacePage* page = reinterpret_cast<NewSpacePage*>(page_start);
+    return page;
+  }
+
+  // Find the page for a limit address. A limit address is either an address
+  // inside a page, or the address right after the last byte of a page.
+  static inline NewSpacePage* FromLimit(Address address_limit) {
+    return NewSpacePage::FromAddress(address_limit - 1);
+  }
+
+  // Checks if address1 and address2 are on the same new space page.
+  static inline bool OnSamePage(Address address1, Address address2) {
+    return NewSpacePage::FromAddress(address1) ==
+           NewSpacePage::FromAddress(address2);
+  }
+
+ private:
+  // Create a NewSpacePage object that is only used as anchor
+  // for the doubly-linked list of real pages.
+  explicit NewSpacePage(SemiSpace* owner) { InitializeAsAnchor(owner); }
+
+  static NewSpacePage* Initialize(Heap* heap, Address start,
+                                  SemiSpace* semi_space);
+
+  // Intialize a fake NewSpacePage used as sentinel at the ends
+  // of a doubly-linked list of real NewSpacePages.
+  // Only uses the prev/next links, and sets flags to not be in new-space.
+  void InitializeAsAnchor(SemiSpace* owner);
+
+  friend class SemiSpace;
+  friend class SemiSpaceIterator;
+};
+
+
+// -----------------------------------------------------------------------------
+// SemiSpace in young generation
+//
+// A semispace is a contiguous chunk of memory holding page-like memory
+// chunks. The mark-compact collector  uses the memory of the first page in
+// the from space as a marking stack when tracing live objects.
+
+class SemiSpace : public Space {
+ public:
+  // Constructor.
+  SemiSpace(Heap* heap, SemiSpaceId semispace)
+      : Space(heap, NEW_SPACE, NOT_EXECUTABLE),
+        start_(NULL),
+        age_mark_(NULL),
+        id_(semispace),
+        anchor_(this),
+        current_page_(NULL) {}
+
+  // Sets up the semispace using the given chunk.
+  void SetUp(Address start, int initial_capacity, int maximum_capacity);
+
+  // Tear down the space.  Heap memory was not allocated by the space, so it
+  // is not deallocated here.
+  void TearDown();
+
+  // True if the space has been set up but not torn down.
+  bool HasBeenSetUp() { return start_ != NULL; }
+
+  // Grow the semispace to the new capacity.  The new capacity
+  // requested must be larger than the current capacity and less than
+  // the maximum capacity.
+  bool GrowTo(int new_capacity);
+
+  // Shrinks the semispace to the new capacity.  The new capacity
+  // requested must be more than the amount of used memory in the
+  // semispace and less than the current capacity.
+  bool ShrinkTo(int new_capacity);
+
+  // Returns the start address of the first page of the space.
+  Address space_start() {
+    DCHECK(anchor_.next_page() != &anchor_);
+    return anchor_.next_page()->area_start();
+  }
+
+  // Returns the start address of the current page of the space.
+  Address page_low() { return current_page_->area_start(); }
+
+  // Returns one past the end address of the space.
+  Address space_end() { return anchor_.prev_page()->area_end(); }
+
+  // Returns one past the end address of the current page of the space.
+  Address page_high() { return current_page_->area_end(); }
+
+  bool AdvancePage() {
+    NewSpacePage* next_page = current_page_->next_page();
+    if (next_page == anchor()) return false;
+    current_page_ = next_page;
+    return true;
+  }
+
+  // Resets the space to using the first page.
+  void Reset();
+
+  // Age mark accessors.
+  Address age_mark() { return age_mark_; }
+  void set_age_mark(Address mark);
+
+  // True if the address is in the address range of this semispace (not
+  // necessarily below the allocation pointer).
+  bool Contains(Address a) {
+    return (reinterpret_cast<uintptr_t>(a) & address_mask_) ==
+           reinterpret_cast<uintptr_t>(start_);
+  }
+
+  // True if the object is a heap object in the address range of this
+  // semispace (not necessarily below the allocation pointer).
+  bool Contains(Object* o) {
+    return (reinterpret_cast<uintptr_t>(o) & object_mask_) == object_expected_;
+  }
+
+  // If we don't have these here then SemiSpace will be abstract.  However
+  // they should never be called.
+  virtual intptr_t Size() {
+    UNREACHABLE();
+    return 0;
+  }
+
+  bool is_committed() { return committed_; }
+  bool Commit();
+  bool Uncommit();
+
+  NewSpacePage* first_page() { return anchor_.next_page(); }
+  NewSpacePage* current_page() { return current_page_; }
+
+#ifdef VERIFY_HEAP
+  virtual void Verify();
+#endif
+
+#ifdef DEBUG
+  virtual void Print();
+  // Validate a range of of addresses in a SemiSpace.
+  // The "from" address must be on a page prior to the "to" address,
+  // in the linked page order, or it must be earlier on the same page.
+  static void AssertValidRange(Address from, Address to);
+#else
+  // Do nothing.
+  inline static void AssertValidRange(Address from, Address to) {}
+#endif
+
+  // Returns the current total capacity of the semispace.
+  int TotalCapacity() { return total_capacity_; }
+
+  // Returns the maximum total capacity of the semispace.
+  int MaximumTotalCapacity() { return maximum_total_capacity_; }
+
+  // Returns the initial capacity of the semispace.
+  int InitialTotalCapacity() { return initial_total_capacity_; }
+
+  SemiSpaceId id() { return id_; }
+
+  static void Swap(SemiSpace* from, SemiSpace* to);
+
+  // Returns the maximum amount of memory ever committed by the semi space.
+  size_t MaximumCommittedMemory() { return maximum_committed_; }
+
+  // Approximate amount of physical memory committed for this space.
+  size_t CommittedPhysicalMemory();
+
+ private:
+  // Flips the semispace between being from-space and to-space.
+  // Copies the flags into the masked positions on all pages in the space.
+  void FlipPages(intptr_t flags, intptr_t flag_mask);
+
+  // Updates Capacity and MaximumCommitted based on new capacity.
+  void SetCapacity(int new_capacity);
+
+  NewSpacePage* anchor() { return &anchor_; }
+
+  // The current and maximum total capacity of the space.
+  int total_capacity_;
+  int maximum_total_capacity_;
+  int initial_total_capacity_;
+
+  intptr_t maximum_committed_;
+
+  // The start address of the space.
+  Address start_;
+  // Used to govern object promotion during mark-compact collection.
+  Address age_mark_;
+
+  // Masks and comparison values to test for containment in this semispace.
+  uintptr_t address_mask_;
+  uintptr_t object_mask_;
+  uintptr_t object_expected_;
+
+  bool committed_;
+  SemiSpaceId id_;
+
+  NewSpacePage anchor_;
+  NewSpacePage* current_page_;
+
+  friend class SemiSpaceIterator;
+  friend class NewSpacePageIterator;
+
+ public:
+  TRACK_MEMORY("SemiSpace")
+};
+
+
+// A SemiSpaceIterator is an ObjectIterator that iterates over the active
+// semispace of the heap's new space.  It iterates over the objects in the
+// semispace from a given start address (defaulting to the bottom of the
+// semispace) to the top of the semispace.  New objects allocated after the
+// iterator is created are not iterated.
+class SemiSpaceIterator : public ObjectIterator {
+ public:
+  // Create an iterator over the objects in the given space.  If no start
+  // address is given, the iterator starts from the bottom of the space.  If
+  // no size function is given, the iterator calls Object::Size().
+
+  // Iterate over all of allocated to-space.
+  explicit SemiSpaceIterator(NewSpace* space);
+  // Iterate over all of allocated to-space, with a custome size function.
+  SemiSpaceIterator(NewSpace* space, HeapObjectCallback size_func);
+  // Iterate over part of allocated to-space, from start to the end
+  // of allocation.
+  SemiSpaceIterator(NewSpace* space, Address start);
+  // Iterate from one address to another in the same semi-space.
+  SemiSpaceIterator(Address from, Address to);
+
+  HeapObject* Next() {
+    if (current_ == limit_) return NULL;
+    if (NewSpacePage::IsAtEnd(current_)) {
+      NewSpacePage* page = NewSpacePage::FromLimit(current_);
+      page = page->next_page();
+      DCHECK(!page->is_anchor());
+      current_ = page->area_start();
+      if (current_ == limit_) return NULL;
+    }
+
+    HeapObject* object = HeapObject::FromAddress(current_);
+    int size = (size_func_ == NULL) ? object->Size() : size_func_(object);
+
+    current_ += size;
+    return object;
+  }
+
+  // Implementation of the ObjectIterator functions.
+  virtual HeapObject* next_object() { return Next(); }
+
+ private:
+  void Initialize(Address start, Address end, HeapObjectCallback size_func);
+
+  // The current iteration point.
+  Address current_;
+  // The end of iteration.
+  Address limit_;
+  // The callback function.
+  HeapObjectCallback size_func_;
+};
+
+
+// -----------------------------------------------------------------------------
+// A PageIterator iterates the pages in a semi-space.
+class NewSpacePageIterator BASE_EMBEDDED {
+ public:
+  // Make an iterator that runs over all pages in to-space.
+  explicit inline NewSpacePageIterator(NewSpace* space);
+
+  // Make an iterator that runs over all pages in the given semispace,
+  // even those not used in allocation.
+  explicit inline NewSpacePageIterator(SemiSpace* space);
+
+  // Make iterator that iterates from the page containing start
+  // to the page that contains limit in the same semispace.
+  inline NewSpacePageIterator(Address start, Address limit);
+
+  inline bool has_next();
+  inline NewSpacePage* next();
+
+ private:
+  NewSpacePage* prev_page_;  // Previous page returned.
+  // Next page that will be returned.  Cached here so that we can use this
+  // iterator for operations that deallocate pages.
+  NewSpacePage* next_page_;
+  // Last page returned.
+  NewSpacePage* last_page_;
+};
+
+
+// -----------------------------------------------------------------------------
+// The young generation space.
+//
+// The new space consists of a contiguous pair of semispaces.  It simply
+// forwards most functions to the appropriate semispace.
+
+class NewSpace : public Space {
+ public:
+  // Constructor.
+  explicit NewSpace(Heap* heap)
+      : Space(heap, NEW_SPACE, NOT_EXECUTABLE),
+        to_space_(heap, kToSpace),
+        from_space_(heap, kFromSpace),
+        reservation_(),
+        inline_allocation_limit_step_(0) {}
+
+  // Sets up the new space using the given chunk.
+  bool SetUp(int reserved_semispace_size_, int max_semi_space_size);
+
+  // Tears down the space.  Heap memory was not allocated by the space, so it
+  // is not deallocated here.
+  void TearDown();
+
+  // True if the space has been set up but not torn down.
+  bool HasBeenSetUp() {
+    return to_space_.HasBeenSetUp() && from_space_.HasBeenSetUp();
+  }
+
+  // Flip the pair of spaces.
+  void Flip();
+
+  // Grow the capacity of the semispaces.  Assumes that they are not at
+  // their maximum capacity.
+  void Grow();
+
+  // Shrink the capacity of the semispaces.
+  void Shrink();
+
+  // True if the address or object lies in the address range of either
+  // semispace (not necessarily below the allocation pointer).
+  bool Contains(Address a) {
+    return (reinterpret_cast<uintptr_t>(a) & address_mask_) ==
+           reinterpret_cast<uintptr_t>(start_);
+  }
+
+  bool Contains(Object* o) {
+    Address a = reinterpret_cast<Address>(o);
+    return (reinterpret_cast<uintptr_t>(a) & object_mask_) == object_expected_;
+  }
+
+  // Return the allocated bytes in the active semispace.
+  virtual intptr_t Size() {
+    return pages_used_ * NewSpacePage::kAreaSize +
+           static_cast<int>(top() - to_space_.page_low());
+  }
+
+  // The same, but returning an int.  We have to have the one that returns
+  // intptr_t because it is inherited, but if we know we are dealing with the
+  // new space, which can't get as big as the other spaces then this is useful:
+  int SizeAsInt() { return static_cast<int>(Size()); }
+
+  // Return the allocatable capacity of a semispace.
+  intptr_t Capacity() {
+    SLOW_DCHECK(to_space_.TotalCapacity() == from_space_.TotalCapacity());
+    return (to_space_.TotalCapacity() / Page::kPageSize) *
+           NewSpacePage::kAreaSize;
+  }
+
+  // Return the current size of a semispace, allocatable and non-allocatable
+  // memory.
+  intptr_t TotalCapacity() {
+    DCHECK(to_space_.TotalCapacity() == from_space_.TotalCapacity());
+    return to_space_.TotalCapacity();
+  }
+
+  // Return the total amount of memory committed for new space.
+  intptr_t CommittedMemory() {
+    if (from_space_.is_committed()) return 2 * Capacity();
+    return TotalCapacity();
+  }
+
+  // Return the total amount of memory committed for new space.
+  intptr_t MaximumCommittedMemory() {
+    return to_space_.MaximumCommittedMemory() +
+           from_space_.MaximumCommittedMemory();
+  }
+
+  // Approximate amount of physical memory committed for this space.
+  size_t CommittedPhysicalMemory();
+
+  // Return the available bytes without growing.
+  intptr_t Available() { return Capacity() - Size(); }
+
+  // Return the maximum capacity of a semispace.
+  int MaximumCapacity() {
+    DCHECK(to_space_.MaximumTotalCapacity() ==
+           from_space_.MaximumTotalCapacity());
+    return to_space_.MaximumTotalCapacity();
+  }
+
+  bool IsAtMaximumCapacity() { return TotalCapacity() == MaximumCapacity(); }
+
+  // Returns the initial capacity of a semispace.
+  int InitialTotalCapacity() {
+    DCHECK(to_space_.InitialTotalCapacity() ==
+           from_space_.InitialTotalCapacity());
+    return to_space_.InitialTotalCapacity();
+  }
+
+  // Return the address of the allocation pointer in the active semispace.
+  Address top() {
+    DCHECK(to_space_.current_page()->ContainsLimit(allocation_info_.top()));
+    return allocation_info_.top();
+  }
+
+  void set_top(Address top) {
+    DCHECK(to_space_.current_page()->ContainsLimit(top));
+    allocation_info_.set_top(top);
+  }
+
+  // Return the address of the allocation pointer limit in the active semispace.
+  Address limit() {
+    DCHECK(to_space_.current_page()->ContainsLimit(allocation_info_.limit()));
+    return allocation_info_.limit();
+  }
+
+  // Return the address of the first object in the active semispace.
+  Address bottom() { return to_space_.space_start(); }
+
+  // Get the age mark of the inactive semispace.
+  Address age_mark() { return from_space_.age_mark(); }
+  // Set the age mark in the active semispace.
+  void set_age_mark(Address mark) { to_space_.set_age_mark(mark); }
+
+  // The start address of the space and a bit mask. Anding an address in the
+  // new space with the mask will result in the start address.
+  Address start() { return start_; }
+  uintptr_t mask() { return address_mask_; }
+
+  INLINE(uint32_t AddressToMarkbitIndex(Address addr)) {
+    DCHECK(Contains(addr));
+    DCHECK(IsAligned(OffsetFrom(addr), kPointerSize) ||
+           IsAligned(OffsetFrom(addr) - 1, kPointerSize));
+    return static_cast<uint32_t>(addr - start_) >> kPointerSizeLog2;
+  }
+
+  INLINE(Address MarkbitIndexToAddress(uint32_t index)) {
+    return reinterpret_cast<Address>(index << kPointerSizeLog2);
+  }
+
+  // The allocation top and limit address.
+  Address* allocation_top_address() { return allocation_info_.top_address(); }
+
+  // The allocation limit address.
+  Address* allocation_limit_address() {
+    return allocation_info_.limit_address();
+  }
+
+  MUST_USE_RESULT INLINE(AllocationResult AllocateRaw(int size_in_bytes));
+
+  // Reset the allocation pointer to the beginning of the active semispace.
+  void ResetAllocationInfo();
+
+  void UpdateInlineAllocationLimit(int size_in_bytes);
+  void LowerInlineAllocationLimit(intptr_t step) {
+    inline_allocation_limit_step_ = step;
+    UpdateInlineAllocationLimit(0);
+    top_on_previous_step_ = allocation_info_.top();
+  }
+
+  // Get the extent of the inactive semispace (for use as a marking stack,
+  // or to zap it). Notice: space-addresses are not necessarily on the
+  // same page, so FromSpaceStart() might be above FromSpaceEnd().
+  Address FromSpacePageLow() { return from_space_.page_low(); }
+  Address FromSpacePageHigh() { return from_space_.page_high(); }
+  Address FromSpaceStart() { return from_space_.space_start(); }
+  Address FromSpaceEnd() { return from_space_.space_end(); }
+
+  // Get the extent of the active semispace's pages' memory.
+  Address ToSpaceStart() { return to_space_.space_start(); }
+  Address ToSpaceEnd() { return to_space_.space_end(); }
+
+  inline bool ToSpaceContains(Address address) {
+    return to_space_.Contains(address);
+  }
+  inline bool FromSpaceContains(Address address) {
+    return from_space_.Contains(address);
+  }
+
+  // True if the object is a heap object in the address range of the
+  // respective semispace (not necessarily below the allocation pointer of the
+  // semispace).
+  inline bool ToSpaceContains(Object* o) { return to_space_.Contains(o); }
+  inline bool FromSpaceContains(Object* o) { return from_space_.Contains(o); }
+
+  // Try to switch the active semispace to a new, empty, page.
+  // Returns false if this isn't possible or reasonable (i.e., there
+  // are no pages, or the current page is already empty), or true
+  // if successful.
+  bool AddFreshPage();
+
+#ifdef VERIFY_HEAP
+  // Verify the active semispace.
+  virtual void Verify();
+#endif
+
+#ifdef DEBUG
+  // Print the active semispace.
+  virtual void Print() { to_space_.Print(); }
+#endif
+
+  // Iterates the active semispace to collect statistics.
+  void CollectStatistics();
+  // Reports previously collected statistics of the active semispace.
+  void ReportStatistics();
+  // Clears previously collected statistics.
+  void ClearHistograms();
+
+  // Record the allocation or promotion of a heap object.  Note that we don't
+  // record every single allocation, but only those that happen in the
+  // to space during a scavenge GC.
+  void RecordAllocation(HeapObject* obj);
+  void RecordPromotion(HeapObject* obj);
+
+  // Return whether the operation succeded.
+  bool CommitFromSpaceIfNeeded() {
+    if (from_space_.is_committed()) return true;
+    return from_space_.Commit();
+  }
+
+  bool UncommitFromSpace() {
+    if (!from_space_.is_committed()) return true;
+    return from_space_.Uncommit();
+  }
+
+  inline intptr_t inline_allocation_limit_step() {
+    return inline_allocation_limit_step_;
+  }
+
+  SemiSpace* active_space() { return &to_space_; }
+
+ private:
+  // Update allocation info to match the current to-space page.
+  void UpdateAllocationInfo();
+
+  Address chunk_base_;
+  uintptr_t chunk_size_;
+
+  // The semispaces.
+  SemiSpace to_space_;
+  SemiSpace from_space_;
+  base::VirtualMemory reservation_;
+  int pages_used_;
+
+  // Start address and bit mask for containment testing.
+  Address start_;
+  uintptr_t address_mask_;
+  uintptr_t object_mask_;
+  uintptr_t object_expected_;
+
+  // Allocation pointer and limit for normal allocation and allocation during
+  // mark-compact collection.
+  AllocationInfo allocation_info_;
+
+  // When incremental marking is active we will set allocation_info_.limit
+  // to be lower than actual limit and then will gradually increase it
+  // in steps to guarantee that we do incremental marking steps even
+  // when all allocation is performed from inlined generated code.
+  intptr_t inline_allocation_limit_step_;
+
+  Address top_on_previous_step_;
+
+  HistogramInfo* allocated_histogram_;
+  HistogramInfo* promoted_histogram_;
+
+  MUST_USE_RESULT AllocationResult SlowAllocateRaw(int size_in_bytes);
+
+  friend class SemiSpaceIterator;
+
+ public:
+  TRACK_MEMORY("NewSpace")
+};
+
+
+// -----------------------------------------------------------------------------
+// Old object space (excluding map objects)
+
+class OldSpace : public PagedSpace {
+ public:
+  // Creates an old space object with a given maximum capacity.
+  // The constructor does not allocate pages from OS.
+  OldSpace(Heap* heap, intptr_t max_capacity, AllocationSpace id,
+           Executability executable)
+      : PagedSpace(heap, max_capacity, id, executable) {}
+
+ public:
+  TRACK_MEMORY("OldSpace")
+};
+
+
+// For contiguous spaces, top should be in the space (or at the end) and limit
+// should be the end of the space.
+#define DCHECK_SEMISPACE_ALLOCATION_INFO(info, space) \
+  SLOW_DCHECK((space).page_low() <= (info).top() &&   \
+              (info).top() <= (space).page_high() &&  \
+              (info).limit() <= (space).page_high())
+
+
+// -----------------------------------------------------------------------------
+// Old space for all map objects
+
+class MapSpace : public PagedSpace {
+ public:
+  // Creates a map space object with a maximum capacity.
+  MapSpace(Heap* heap, intptr_t max_capacity, AllocationSpace id)
+      : PagedSpace(heap, max_capacity, id, NOT_EXECUTABLE),
+        max_map_space_pages_(kMaxMapPageIndex - 1) {}
+
+  // Given an index, returns the page address.
+  // TODO(1600): this limit is artifical just to keep code compilable
+  static const int kMaxMapPageIndex = 1 << 16;
+
+  virtual int RoundSizeDownToObjectAlignment(int size) {
+    if (base::bits::IsPowerOfTwo32(Map::kSize)) {
+      return RoundDown(size, Map::kSize);
+    } else {
+      return (size / Map::kSize) * Map::kSize;
+    }
+  }
+
+ protected:
+  virtual void VerifyObject(HeapObject* obj);
+
+ private:
+  static const int kMapsPerPage = Page::kMaxRegularHeapObjectSize / Map::kSize;
+
+  // Do map space compaction if there is a page gap.
+  int CompactionThreshold() {
+    return kMapsPerPage * (max_map_space_pages_ - 1);
+  }
+
+  const int max_map_space_pages_;
+
+ public:
+  TRACK_MEMORY("MapSpace")
+};
+
+
+// -----------------------------------------------------------------------------
+// Old space for simple property cell objects
+
+class CellSpace : public PagedSpace {
+ public:
+  // Creates a property cell space object with a maximum capacity.
+  CellSpace(Heap* heap, intptr_t max_capacity, AllocationSpace id)
+      : PagedSpace(heap, max_capacity, id, NOT_EXECUTABLE) {}
+
+  virtual int RoundSizeDownToObjectAlignment(int size) {
+    if (base::bits::IsPowerOfTwo32(Cell::kSize)) {
+      return RoundDown(size, Cell::kSize);
+    } else {
+      return (size / Cell::kSize) * Cell::kSize;
+    }
+  }
+
+ protected:
+  virtual void VerifyObject(HeapObject* obj);
+
+ public:
+  TRACK_MEMORY("CellSpace")
+};
+
+
+// -----------------------------------------------------------------------------
+// Old space for all global object property cell objects
+
+class PropertyCellSpace : public PagedSpace {
+ public:
+  // Creates a property cell space object with a maximum capacity.
+  PropertyCellSpace(Heap* heap, intptr_t max_capacity, AllocationSpace id)
+      : PagedSpace(heap, max_capacity, id, NOT_EXECUTABLE) {}
+
+  virtual int RoundSizeDownToObjectAlignment(int size) {
+    if (base::bits::IsPowerOfTwo32(PropertyCell::kSize)) {
+      return RoundDown(size, PropertyCell::kSize);
+    } else {
+      return (size / PropertyCell::kSize) * PropertyCell::kSize;
+    }
+  }
+
+ protected:
+  virtual void VerifyObject(HeapObject* obj);
+
+ public:
+  TRACK_MEMORY("PropertyCellSpace")
+};
+
+
+// -----------------------------------------------------------------------------
+// Large objects ( > Page::kMaxHeapObjectSize ) are allocated and managed by
+// the large object space. A large object is allocated from OS heap with
+// extra padding bytes (Page::kPageSize + Page::kObjectStartOffset).
+// A large object always starts at Page::kObjectStartOffset to a page.
+// Large objects do not move during garbage collections.
+
+class LargeObjectSpace : public Space {
+ public:
+  LargeObjectSpace(Heap* heap, intptr_t max_capacity, AllocationSpace id);
+  virtual ~LargeObjectSpace() {}
+
+  // Initializes internal data structures.
+  bool SetUp();
+
+  // Releases internal resources, frees objects in this space.
+  void TearDown();
+
+  static intptr_t ObjectSizeFor(intptr_t chunk_size) {
+    if (chunk_size <= (Page::kPageSize + Page::kObjectStartOffset)) return 0;
+    return chunk_size - Page::kPageSize - Page::kObjectStartOffset;
+  }
+
+  // Shared implementation of AllocateRaw, AllocateRawCode and
+  // AllocateRawFixedArray.
+  MUST_USE_RESULT AllocationResult
+      AllocateRaw(int object_size, Executability executable);
+
+  // Available bytes for objects in this space.
+  inline intptr_t Available();
+
+  virtual intptr_t Size() { return size_; }
+
+  virtual intptr_t SizeOfObjects() { return objects_size_; }
+
+  intptr_t MaximumCommittedMemory() { return maximum_committed_; }
+
+  intptr_t CommittedMemory() { return Size(); }
+
+  // Approximate amount of physical memory committed for this space.
+  size_t CommittedPhysicalMemory();
+
+  int PageCount() { return page_count_; }
+
+  // Finds an object for a given address, returns a Smi if it is not found.
+  // The function iterates through all objects in this space, may be slow.
+  Object* FindObject(Address a);
+
+  // Finds a large object page containing the given address, returns NULL
+  // if such a page doesn't exist.
+  LargePage* FindPage(Address a);
+
+  // Frees unmarked objects.
+  void FreeUnmarkedObjects();
+
+  // Checks whether a heap object is in this space; O(1).
+  bool Contains(HeapObject* obj);
+
+  // Checks whether the space is empty.
+  bool IsEmpty() { return first_page_ == NULL; }
+
+  LargePage* first_page() { return first_page_; }
+
+#ifdef VERIFY_HEAP
+  virtual void Verify();
+#endif
+
+#ifdef DEBUG
+  virtual void Print();
+  void ReportStatistics();
+  void CollectCodeStatistics();
+#endif
+  // Checks whether an address is in the object area in this space.  It
+  // iterates all objects in the space. May be slow.
+  bool SlowContains(Address addr) { return FindObject(addr)->IsHeapObject(); }
+
+ private:
+  intptr_t max_capacity_;
+  intptr_t maximum_committed_;
+  // The head of the linked list of large object chunks.
+  LargePage* first_page_;
+  intptr_t size_;          // allocated bytes
+  int page_count_;         // number of chunks
+  intptr_t objects_size_;  // size of objects
+  // Map MemoryChunk::kAlignment-aligned chunks to large pages covering them
+  HashMap chunk_map_;
+
+  friend class LargeObjectIterator;
+
+ public:
+  TRACK_MEMORY("LargeObjectSpace")
+};
+
+
+class LargeObjectIterator : public ObjectIterator {
+ public:
+  explicit LargeObjectIterator(LargeObjectSpace* space);
+  LargeObjectIterator(LargeObjectSpace* space, HeapObjectCallback size_func);
+
+  HeapObject* Next();
+
+  // implementation of ObjectIterator.
+  virtual HeapObject* next_object() { return Next(); }
+
+ private:
+  LargePage* current_;
+  HeapObjectCallback size_func_;
+};
+
+
+// Iterates over the chunks (pages and large object pages) that can contain
+// pointers to new space.
+class PointerChunkIterator BASE_EMBEDDED {
+ public:
+  inline explicit PointerChunkIterator(Heap* heap);
+
+  // Return NULL when the iterator is done.
+  MemoryChunk* next() {
+    switch (state_) {
+      case kOldPointerState: {
+        if (old_pointer_iterator_.has_next()) {
+          return old_pointer_iterator_.next();
+        }
+        state_ = kMapState;
+        // Fall through.
+      }
+      case kMapState: {
+        if (map_iterator_.has_next()) {
+          return map_iterator_.next();
+        }
+        state_ = kLargeObjectState;
+        // Fall through.
+      }
+      case kLargeObjectState: {
+        HeapObject* heap_object;
+        do {
+          heap_object = lo_iterator_.Next();
+          if (heap_object == NULL) {
+            state_ = kFinishedState;
+            return NULL;
+          }
+          // Fixed arrays are the only pointer-containing objects in large
+          // object space.
+        } while (!heap_object->IsFixedArray());
+        MemoryChunk* answer = MemoryChunk::FromAddress(heap_object->address());
+        return answer;
+      }
+      case kFinishedState:
+        return NULL;
+      default:
+        break;
+    }
+    UNREACHABLE();
+    return NULL;
+  }
+
+
+ private:
+  enum State { kOldPointerState, kMapState, kLargeObjectState, kFinishedState };
+  State state_;
+  PageIterator old_pointer_iterator_;
+  PageIterator map_iterator_;
+  LargeObjectIterator lo_iterator_;
+};
+
+
+#ifdef DEBUG
+struct CommentStatistic {
+  const char* comment;
+  int size;
+  int count;
+  void Clear() {
+    comment = NULL;
+    size = 0;
+    count = 0;
+  }
+  // Must be small, since an iteration is used for lookup.
+  static const int kMaxComments = 64;
+};
+#endif
+}
+}  // namespace v8::internal
+
+#endif  // V8_HEAP_SPACES_H_