Change LookupForWrite to always do a full lookup and check the result.

src/property.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 344 matching lines @@
       case HANDLER:
       case INTERCEPTOR:
       case TRANSITION:
       case NONEXISTENT:
         return isolate()->heap()->the_hole_value();
     }
     UNREACHABLE();
     return NULL;
   }
 
+  Map* GetTransitionTarget(Map* map) {
+    ASSERT(IsTransition());
+    TransitionArray* transitions = map->transitions();
+    return transitions->GetTarget(number_);
+  }
+
   Map* GetTransitionTarget() {
-    ASSERT(IsTransition());
-    TransitionArray* transitions = holder()->map()->transitions();
-    return transitions->GetTarget(number_);
+    return GetTransitionTarget(holder()->map());
   }
 
   PropertyDetails GetTransitionDetails(Map* map) {
     ASSERT(IsTransition());
     TransitionArray* transitions = map->transitions();
     return transitions->GetTargetDetails(number_);
   }
 
   PropertyDetails GetTransitionDetails() {
     return GetTransitionDetails(holder()->map());
@@ skipping 94 matching lines @@
   JSReceiver* holder_;
   int number_;
   bool cacheable_;
   PropertyDetails details_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_PROPERTY_H_