Introduce EmbedderHeapTracer

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 8802266d985654b1e4792f5cddb6fafd409e32da..2751d41dbc764741ec15fa4cdf7ae961a211cbf8 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -68,7 +68,6 @@ class IdleScavengeObserver : public AllocationObserver {
   Heap& heap_;
 };
 
-
 Heap::Heap()
     : amount_of_external_allocated_memory_(0),
       amount_of_external_allocated_memory_at_last_global_gc_(0),
@@ -116,6 +115,7 @@ Heap::Heap()
       inline_allocation_disabled_(false),
       total_regexp_code_generated_(0),
       tracer_(nullptr),
+      embedder_heap_tracer_(nullptr),
       high_survival_rate_period_length_(0),
       promoted_objects_size_(0),
       promotion_ratio_(0),
@@ -1303,6 +1303,11 @@ bool Heap::PerformGarbageCollection(
       UpdateOldGenerationAllocationCounter();
       // Perform mark-sweep with optional compaction.
       MarkCompact();
+      if (embedder_heap_tracer()) {
+        embedder_heap_tracer()->ClearTracingMarks(
+            reinterpret_cast<v8::Isolate*>(isolate()));
+      }
+
       old_gen_exhausted_ = false;
       old_generation_size_configured_ = true;
       // This should be updated before PostGarbageCollectionProcessing, which
@@ -5518,6 +5523,15 @@ void Heap::RemoveGCEpilogueCallback(v8::Isolate::GCCallback callback) {
   UNREACHABLE();
 }
 
+void Heap::SetEmbedderHeapTracer(EmbedderHeapTracer* tracer) {
+  DCHECK(tracer != nullptr);
+  embedder_heap_tracer_ = tracer;
+}
+
+void Heap::UnsetEmbedderHeapTracer() {
+  DCHECK(embedder_heap_tracer_ != nullptr);
+  embedder_heap_tracer_ = nullptr;
+}
 
 // TODO(ishell): Find a better place for this.
 void Heap::AddWeakObjectToCodeDependency(Handle<HeapObject> obj,