Optimize ClearNonLiveReferences: do not compact prototype transitions in GC.

src/transitions.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_TRANSITIONS_H_
 #define V8_TRANSITIONS_H_
 
 #include "src/checks.h"
 #include "src/elements-kind.h"
 #include "src/heap/heap.h"
@@ skipping 95 matching lines @@
   static Handle<Map> GetPrototypeTransition(Handle<Map> map,
                                             Handle<Object> prototype);
 
   static FixedArray* GetPrototypeTransitions(Map* map);
 
   static int NumberOfPrototypeTransitions(FixedArray* proto_transitions) {
     if (proto_transitions->length() == 0) return 0;
     Object* raw = proto_transitions->get(kProtoTransitionNumberOfEntriesOffset);
     return Smi::cast(raw)->value();
   }
+  static int NumberOfPrototypeTransitionsForTest(Map* map);
 
   static void SetNumberOfPrototypeTransitions(FixedArray* proto_transitions,
                                               int value);
 
   inline FixedArray* GetPrototypeTransitions();
   inline void SetPrototypeTransitions(
       FixedArray* prototype_transitions,
       WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
   inline Object** GetPrototypeTransitionsSlot();
   inline bool HasPrototypeTransitions();
@@ skipping 139 matching lines @@
     return transition->instance_descriptors()->GetKey(descriptor);
   }
 
   static void TraverseTransitionTreeInternal(Map* map,
                                              TraverseCallback callback,
                                              void* data);
 
   static void SetPrototypeTransitions(Handle<Map> map,
                                       Handle<FixedArray> proto_transitions);
 
+  static bool CompactPrototypeTransitionArray(FixedArray* array);
+
+  static Handle<FixedArray> GrowPrototypeTransitionArray(
+      Handle<FixedArray> array, int new_capacity, Isolate* isolate);
+
   // Compares two tuples <key, kind, attributes>, returns -1 if
   // tuple1 is "less" than tuple2, 0 if tuple1 equal to tuple2 and 1 otherwise.
   static inline int CompareKeys(Name* key1, uint32_t hash1, PropertyKind kind1,
                                 PropertyAttributes attributes1, Name* key2,
                                 uint32_t hash2, PropertyKind kind2,
                                 PropertyAttributes attributes2);
 
   // Compares keys, returns -1 if key1 is "less" than key2,
   // 0 if key1 equal to key2 and 1 otherwise.
   static inline int CompareNames(Name* key1, uint32_t hash1, Name* key2,
@@ skipping 22 matching lines @@
 #endif
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(TransitionArray);
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TRANSITIONS_H_