Add a flag to over approximate the weak closure during GC

src/heap/mark-compact.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_MARK_COMPACT_H_
 #define V8_HEAP_MARK_COMPACT_H_
 
 #include "src/base/bits.h"
 #include "src/heap/spaces.h"
 
@@ skipping 649 matching lines @@
   void MarkAllocationSite(AllocationSite* site);
 
   MarkingDeque* marking_deque() { return &marking_deque_; }
 
   void EnsureMarkingDequeIsCommittedAndInitialize();
 
   void InitializeMarkingDeque();
 
   void UncommitMarkingDeque();
 
+  void OverApproximateWeakClosure();
+
  private:
   class SweeperTask;
 
   explicit MarkCompactCollector(Heap* heap);
   ~MarkCompactCollector();
 
   bool MarkInvalidatedCode();
   bool WillBeDeoptimized(Code* code);
   void RemoveDeadInvalidatedCode();
   void ProcessInvalidatedCode(ObjectVisitor* visitor);
@@ skipping 276 matching lines @@
  private:
   MarkCompactCollector* collector_;
 };
 
 
 const char* AllocationSpaceName(AllocationSpace space);
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_MARK_COMPACT_H_