Introduce EmbedderHeapTracer

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 3226828c2210436afae35a0440bc489d349aa705..c84418c09f3ef30dd6268e953a86642afeeb792b 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -605,6 +605,8 @@ class Heap {
   // should not happen during deserialization.
   void NotifyDeserializationComplete();
 
+  void AddObjectToMarkingDeque(Object** object);
+
   intptr_t old_generation_allocation_limit() const {
     return old_generation_allocation_limit_;
   }
@@ -923,6 +925,7 @@ class Heap {
   // ===========================================================================
 
   GCTracer* tracer() { return tracer_; }
+  EmbedderHeapTracer* embedder_heap_tracer() { return embedder_heap_tracer_; }
 
   PromotionQueue* promotion_queue() { return &promotion_queue_; }
 
@@ -1320,6 +1323,8 @@ class Heap {
   void CallGCPrologueCallbacks(GCType gc_type, GCCallbackFlags flags);
   void CallGCEpilogueCallbacks(GCType gc_type, GCCallbackFlags flags);
 
+  void SetEmbedderHeapTracer(EmbedderHeapTracer* tracer);
+
   // ===========================================================================
   // Allocation methods. =======================================================
   // ===========================================================================
@@ -2102,6 +2107,7 @@ 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_;