[heap] Add basic infrastructure for incremental wrapper tracing.

src/heap/mark-compact.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_MARK_COMPACT_H_
 #define V8_HEAP_MARK_COMPACT_H_
 
 #include <deque>
 
 #include "src/base/bits.h"
@@ skipping 482 matching lines @@
   void RegisterWrappersWithEmbedderHeapTracer();
 
   void SetEmbedderHeapTracer(EmbedderHeapTracer* tracer);
 
   EmbedderHeapTracer* embedder_heap_tracer() { return embedder_heap_tracer_; }
 
   bool UsingEmbedderHeapTracer() { return embedder_heap_tracer(); }
 
   void TracePossibleWrapper(JSObject* js_object);
 
-  void RegisterExternallyReferencedObject(Object** object);
-
  private:
   class EvacuateNewSpacePageVisitor;
   class EvacuateNewSpaceVisitor;
   class EvacuateOldSpaceVisitor;
   class EvacuateRecordOnlyVisitor;
   class EvacuateVisitorBase;
   class HeapObjectVisitor;
   class ObjectStatsVisitor;
 
   explicit MarkCompactCollector(Heap* heap);
@@ skipping 254 matching lines @@
  private:
   MarkCompactCollector* collector_;
 };
 
 
 const char* AllocationSpaceName(AllocationSpace space);
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_MARK_COMPACT_H_