Optimize ClearNonLiveReferences: do not compact prototype transitions in 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 638 matching lines @@
   void DiscoverGreyObjectsInSpace(PagedSpace* space);
   void DiscoverGreyObjectsInNewSpace();
 
   // Callback function for telling whether the object *p is an unmarked
   // heap object.
   static bool IsUnmarkedHeapObject(Object** p);
 
   // Map transitions from a live map to a dead map must be killed.
   // We replace them with a null descriptor, with the same key.
   void ClearNonLiveReferences();
-  void ClearNonLivePrototypeTransitions(Map* map);
   void ClearNonLiveMapTransitions(Map* map);
   void ClearMapTransitions(Map* map, Map* dead_transition);
   bool ClearMapBackPointer(Map* map);
   void MarkDependentCodeListForDeoptimization(DependentCode* list_head);
   void TrimDescriptorArray(Map* map, DescriptorArray* descriptors,
                            int number_of_own_descriptors);
   void TrimEnumCache(Map* map, DescriptorArray* descriptors);
 
   // Mark all values associated with reachable keys in weak collections
   // encountered so far.  This might push new object or even new weak maps onto
@@ skipping 194 matching lines @@
  private:
   MarkCompactCollector* collector_;
 };
 
 
 const char* AllocationSpaceName(AllocationSpace space);
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_MARK_COMPACT_H_