Layout descriptor sharing issue fixed.

src/layout-descriptor.h

 // Copyright 2014 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_LAYOUT_DESCRIPTOR_H_
 #define V8_LAYOUT_DESCRIPTOR_H_
 
 #include <iosfwd>
 
 #include "src/objects.h"
@@ skipping 35 matching lines @@
 
   V8_INLINE static LayoutDescriptor* cast_gc_safe(Object* object);
 
   // Builds layout descriptor optimized for given |map| by |num_descriptors|
   // elements of given descriptors array. The |map|'s descriptors could be
   // different.
   static Handle<LayoutDescriptor> New(Handle<Map> map,
                                       Handle<DescriptorArray> descriptors,
                                       int num_descriptors);
 
-  // Creates new layout descriptor by appending property with |details| to
-  // |map|'s layout descriptor.
-  static Handle<LayoutDescriptor> Append(Handle<Map> map,
-                                         PropertyDetails details);
+  // Modifies |map|'s layout descriptor or creates a new one if necessary by
+  // appending property with |details| to it.
+  static Handle<LayoutDescriptor> ShareAppend(Handle<Map> map,
+                                              PropertyDetails details);
 
   // Creates new layout descriptor by appending property with |details| to
   // |map|'s layout descriptor and if it is still fast then returns it.
   // Otherwise the |full_layout_descriptor| is returned.
   static Handle<LayoutDescriptor> AppendIfFastOrUseFull(
       Handle<Map> map, PropertyDetails details,
       Handle<LayoutDescriptor> full_layout_descriptor);
 
   // Layout descriptor that corresponds to an object all fields of which are
   // tagged (FastPointerLayout).
@@ skipping 62 matching lines @@
 
  private:
   bool all_fields_tagged_;
   int header_size_;
   LayoutDescriptor* layout_descriptor_;
 };
 }
 }  // namespace v8::internal
 
 #endif  // V8_LAYOUT_DESCRIPTOR_H_