diff --git a/src/gc/mark_sweep.h b/src/gc/mark_sweep.h
index ed74f99..d64439f 100644
--- a/src/gc/mark_sweep.h
+++ b/src/gc/mark_sweep.h
@@ -25,6 +25,7 @@
 
 namespace art {
 
+class Barrier;
 class CheckObjectVisitor;
 class Class;
 class Heap;
@@ -52,9 +53,15 @@
       EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
+  void MarkNonThreadRoots()
+      EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
+
   void MarkConcurrentRoots();
       EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
 
+  void MarkRootsCheckpoint();
+       EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
+
   // Verify that image roots point to only marked objects within the alloc space.
   void VerifyImageRoots() EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
 
@@ -183,6 +190,11 @@
     }
   }
 
+  static void MarkObjectVisitor(const Object* root, void* arg)
+      EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
+
+  Barrier& GetBarrier();
+
  private:
   // Returns true if the object has its bit set in the mark bitmap.
   bool IsMarked(const Object* object) const;
@@ -193,9 +205,6 @@
   static bool IsMarkedArrayCallback(const Object* object, void* arg)
       SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
 
-  static void MarkObjectVisitor(const Object* root, void* arg)
-      EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
-
   static void ReMarkObjectVisitor(const Object* root, void* arg)
       EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
 
@@ -417,6 +426,8 @@
   size_t array_count_;
   size_t other_count_;
 
+  UniquePtr<Barrier> gc_barrier_;
+
   friend class AddIfReachesAllocSpaceVisitor; // Used by mod-union table.
   friend class CheckBitmapVisitor;
   friend class CheckObjectVisitor;