[heap] Color object black on unsafe layout change.

src/heap/incremental-marking.h

 // Copyright 2012 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_INCREMENTAL_MARKING_H_
 #define V8_HEAP_INCREMENTAL_MARKING_H_
 
 #include "src/cancelable-task.h"
 #include "src/execution.h"
 #include "src/heap/heap.h"
@@ skipping 205 matching lines @@
   void RecordWriteSlow(HeapObject* obj, Object** slot, Object* value);
   void RecordWriteIntoCodeSlow(Code* host, RelocInfo* rinfo, Object* value);
   void RecordWriteOfCodeEntrySlow(JSFunction* host, Object** slot, Code* value);
   void RecordCodeTargetPatch(Code* host, Address pc, HeapObject* value);
   void RecordCodeTargetPatch(Address pc, HeapObject* value);
 
   // Returns true if the function succeeds in transitioning the object
   // from white to grey.
   bool WhiteToGreyAndPush(HeapObject* obj);
 
+  // This function is used to color the object black before it undergoes an
+  // unsafe layout change. This is a part of synchronization protocol with
+  // the concurrent marker.
+  void MarkBlackAndPush(HeapObject* obj);
+
   inline void SetOldSpacePageFlags(MemoryChunk* chunk) {
     SetOldSpacePageFlags(chunk, IsMarking(), IsCompacting());
   }
 
   inline void SetNewSpacePageFlags(Page* chunk) {
     SetNewSpacePageFlags(chunk, IsMarking());
   }
 
   bool IsCompacting() { return IsMarking() && is_compacting_; }
 
@@ skipping 113 matching lines @@
 
   Observer new_generation_observer_;
   Observer old_generation_observer_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(IncrementalMarking);
 };
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_INCREMENTAL_MARKING_H_