Use EmbedderHeapTracer instead of object grouping when trace_embedder_heap flag is set

src/heap/heap.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_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 894 matching lines @@
         return lo_space();
       default:
         return paged_space(idx);
     }
   }
 
   // Returns name of the space.
   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);
 
   // ===========================================================================
   // Getters to other components. ==============================================
   // ===========================================================================
 
   GCTracer* tracer() { return tracer_; }
 
   MemoryAllocator* memory_allocator() { return memory_allocator_; }
 
-  EmbedderHeapTracer* embedder_heap_tracer() { return embedder_heap_tracer_; }
-
   PromotionQueue* promotion_queue() { return &promotion_queue_; }
 
   inline Isolate* isolate();
 
   MarkCompactCollector* mark_compact_collector() {
     return mark_compact_collector_;
   }
 
   // ===========================================================================
   // Root set access. ==========================================================
@@ skipping 1156 matching lines @@
 
   List<GCCallbackPair> gc_epilogue_callbacks_;
   List<GCCallbackPair> gc_prologue_callbacks_;
 
   // Total RegExp code ever generated
   double total_regexp_code_generated_;
 
   int deferred_counters_[v8::Isolate::kUseCounterFeatureCount];
 
   GCTracer* tracer_;
-  EmbedderHeapTracer* embedder_heap_tracer_;
 
   int high_survival_rate_period_length_;
   intptr_t promoted_objects_size_;
   double promotion_ratio_;
   double promotion_rate_;
   intptr_t semi_space_copied_object_size_;
   intptr_t previous_semi_space_copied_object_size_;
   double semi_space_copied_rate_;
   int nodes_died_in_new_space_;
   int nodes_copied_in_new_space_;
@@ skipping 542 matching lines @@
   friend class LargeObjectSpace;
   friend class NewSpace;
   friend class PagedSpace;
   DISALLOW_COPY_AND_ASSIGN(AllocationObserver);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_