Use the incremental root marking visitor for overapproximating the weak closure

src/heap/incremental-marking.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_INCREMENTAL_MARKING_H_
 #define V8_HEAP_INCREMENTAL_MARKING_H_
 
 
 #include "src/execution.h"
 #include "src/heap/mark-compact.h"
@@ skipping 171 matching lines @@
   void LeaveNoMarkingScope() { no_marking_scope_depth_--; }
 
   void NotifyIncompleteScanOfObject(int unscanned_bytes) {
     unscanned_bytes_of_large_object_ = unscanned_bytes;
   }
 
   void ClearIdleMarkingDelayCounter();
 
   bool IsIdleMarkingDelayCounterLimitReached();
 
+  // Creates a visitor for marking roots using this incremental marking
+  // instance. Caller takes ownership.
+  ObjectVisitor* CreateRootMarkingVisitor();
+
  private:
   int64_t SpaceLeftInOldSpace();
 
   void SpeedUp();
 
   void ResetStepCounters();
 
   void StartMarking(CompactionFlag flag);
 
   void ActivateIncrementalWriteBarrier(PagedSpace* space);
@@ skipping 42 matching lines @@
   bool weak_closure_was_overapproximated_;
 
   GCRequestType request_type_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(IncrementalMarking);
 };
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_INCREMENTAL_MARKING_H_