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..2d76d43c48da23d066b817dae86108d5ad4c28b6 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -912,11 +912,17 @@ class Heap {
   const char* GetSpaceName(int idx);
 
   // ===========================================================================
-  // API. ======================================================================
+  // Embedder heap tracing. ====================================================
   // ===========================================================================
 
   void SetEmbedderHeapTracer(EmbedderHeapTracer* tracer);
 
+  EmbedderHeapTracer* embedder_heap_tracer() { return embedder_heap_tracer_; }

[Hannes Payer (out of office), 2016/04/07 20:38:31]

Since the tracer is fully used in mark-compact, it should actually live there.

[Marcel Hlopko, 2016/04/08 08:08:09]

Done.

+
+  bool UsingEmbedderHeapTracer() { return embedder_heap_tracer_; }

[Hannes Payer (out of office), 2016/04/07 20:38:30]

Why don't we just check FLAG_trace_object_groups?

[Marcel Hlopko, 2016/04/08 08:08:10]

I removed the flag (or to be more accurrate, moved it to chromium). The embedder
heap tracing feature is now controlled only by the presence of the heap tracer.
If embedder sets it, v8 will use it. If it's nullptr, v8 will use object
grouping.

+
+  void TracePossibleWrapper(JSObject* js_object);
+
   void RegisterExternallyReferencedObject(Object** object);
 
   // ===========================================================================
@@ -927,8 +933,6 @@ 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();