Avoid redundant weak pointer updates after evacuation.

src/heap/heap.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_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 1657 matching lines @@
   void UpdateNewSpaceReferencesInExternalStringTable(
       ExternalStringTableUpdaterCallback updater_func);
 
   void UpdateReferencesInExternalStringTable(
       ExternalStringTableUpdaterCallback updater_func);
 
   void ProcessAllWeakReferences(WeakObjectRetainer* retainer);
   void ProcessYoungWeakReferences(WeakObjectRetainer* retainer);
   void ProcessNativeContexts(WeakObjectRetainer* retainer);
   void ProcessAllocationSites(WeakObjectRetainer* retainer);
+  void ProcessWeakListRoots(WeakObjectRetainer* retainer);
 
   // ===========================================================================
   // GC statistics. ============================================================
   // ===========================================================================
 
   inline intptr_t OldGenerationSpaceAvailable() {
     return old_generation_allocation_limit_ - PromotedTotalSize();
   }
 
   // Returns maximum GC pause.
@@ skipping 936 matching lines @@
   friend class LargeObjectSpace;
   friend class NewSpace;
   friend class PagedSpace;
   DISALLOW_COPY_AND_ASSIGN(AllocationObserver);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_