[heap] Integrate embedder heap tracer into incremental marking

src/heap/mark-compact.h

Index: src/heap/mark-compact.h
diff --git a/src/heap/mark-compact.h b/src/heap/mark-compact.h
index b2c637bc6361aef2cdecde137d276baa1eb6f5ed..78a2abd04c7b794de51cebe11e585aba9059cf2d 100644
--- a/src/heap/mark-compact.h
+++ b/src/heap/mark-compact.h
@@ -490,16 +490,24 @@ class MarkCompactCollector {
 
   Sweeper& sweeper() { return sweeper_; }
 
-  void RegisterWrappersWithEmbedderHeapTracer();
+  // ===========================================================================
+  // Embedder heap tracer support. =============================================
+  // ===========================================================================
 
   void SetEmbedderHeapTracer(EmbedderHeapTracer* tracer);
-
   EmbedderHeapTracer* embedder_heap_tracer() { return embedder_heap_tracer_; }
-
   bool UsingEmbedderHeapTracer() { return embedder_heap_tracer(); }
 
+  // In order to avoid running out of memory we force tracing wrappers if there
+  // are too many of them.
+  bool RequiresImmediateWrapperProcessing();
+
+  void RegisterWrappersWithEmbedderHeapTracer();
+
   void TracePossibleWrapper(JSObject* js_object);
 
+  size_t wrappers_to_trace() { return wrappers_to_trace_.size(); }
+
  private:
   class EvacuateNewSpacePageVisitor;
   class EvacuateNewSpaceVisitor;