Use EmbedderHeapTracer instead of object grouping when trace_embedder_heap flag is set

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 59d7dfcf002f9229018a4965cdc0617eeef70541..c88dcd2bbd618e218a852f6ebd02709b825447cb 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -912,11 +912,15 @@ class Heap {
   const char* GetSpaceName(int idx);
 
   // ===========================================================================
-  // API. ======================================================================
+  // Embedder heap tracing. ====================================================

[Hannes Payer (out of office), 2016/04/08 12:02:09]

Since all components are just used by the mark compact collector, we can just
remove the API completely and just forward everything to
mark_compact_collector()

[Marcel Hlopko, 2016/04/11 10:29:22]

Done.

   // ===========================================================================
 
   void SetEmbedderHeapTracer(EmbedderHeapTracer* tracer);
 
+  bool UsingEmbedderHeapTracer();
+
+  void TracePossibleWrapper(JSObject* js_object);
+
   void RegisterExternallyReferencedObject(Object** object);
 
   // ===========================================================================
@@ -927,8 +931,6 @@ class Heap {
 
   MemoryAllocator* memory_allocator() { return memory_allocator_; }
 
-  EmbedderHeapTracer* embedder_heap_tracer() { return embedder_heap_tracer_; }
-
   PromotionQueue* promotion_queue() { return &promotion_queue_; }
 
   inline Isolate* isolate();
@@ -2105,7 +2107,6 @@ class Heap {
   int deferred_counters_[v8::Isolate::kUseCounterFeatureCount];
 
   GCTracer* tracer_;
-  EmbedderHeapTracer* embedder_heap_tracer_;
 
   int high_survival_rate_period_length_;
   intptr_t promoted_objects_size_;