Update V8 to r5091 as required by WebKit r63859.

Change-Id: I8e35d765e6f6c7f89eccff900e1cabe2d5dd6110
diff --git a/src/heap.h b/src/heap.h
index df3ba0e..18991b4 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -36,8 +36,6 @@
 namespace v8 {
 namespace internal {
 
-// Forward declarations.
-class ZoneScopeInfo;
 
 // Defines all the roots in Heap.
 #define UNCONDITIONAL_STRONG_ROOT_LIST(V)                                      \
@@ -626,7 +624,6 @@
   // object by containing this pointer.
   // Please note this function does not perform a garbage collection.
   static Object* CreateCode(const CodeDesc& desc,
-                            ZoneScopeInfo* sinfo,
                             Code::Flags flags,
                             Handle<Object> self_reference);
 
@@ -774,11 +771,12 @@
                                       DirtyRegionCallback visit_dirty_region,
                                       ObjectSlotCallback callback);
 
-  // Iterate pointers to new space found in memory interval from start to end.
+  // Iterate pointers to from semispace of new space found in memory interval
+  // from start to end.
   // Update dirty marks for page containing start address.
-  static void IterateAndMarkPointersToNewSpace(Address start,
-                                               Address end,
-                                               ObjectSlotCallback callback);
+  static void IterateAndMarkPointersToFromSpace(Address start,
+                                                Address end,
+                                                ObjectSlotCallback callback);
 
   // Iterate pointers to new space found in memory interval from start to end.
   // Return true if pointers to new space was found.
@@ -985,6 +983,8 @@
 
   static void RecordStats(HeapStats* stats);
 
+  static Scavenger GetScavenger(int instance_type, int instance_size);
+
   // Copy block of memory from src to dst. Size of block should be aligned
   // by pointer size.
   static inline void CopyBlock(Address dst, Address src, int byte_size);
@@ -1232,17 +1232,7 @@
     set_instanceof_cache_function(the_hole_value());
   }
 
-  // Helper function used by CopyObject to copy a source object to an
-  // allocated target object and update the forwarding pointer in the source
-  // object.  Returns the target object.
-  static inline HeapObject* MigrateObject(HeapObject* source,
-                                          HeapObject* target,
-                                          int size);
-
 #if defined(DEBUG) || defined(ENABLE_LOGGING_AND_PROFILING)
-  // Record the copy of an object in the NewSpace's statistics.
-  static void RecordCopiedObject(HeapObject* obj);
-
   // Record statistics before and after garbage collection.
   static void ReportStatisticsBeforeGC();
   static void ReportStatisticsAfterGC();