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

src/property.h

Index: src/property.h
diff --git a/src/property.h b/src/property.h
index 546967ac4437c2050bb5cf1b7f2703ee3264658c..bbba8aea60d89f432c3ca4eb52b86726e56baf07 100644
--- a/src/property.h
+++ b/src/property.h
@@ -362,12 +362,16 @@ class LookupResult BASE_EMBEDDED {
     return NULL;
   }
 
-  Map* GetTransitionTarget() {
+  Map* GetTransitionTarget(Map* map) {
     ASSERT(IsTransition());
-    TransitionArray* transitions = holder()->map()->transitions();
+    TransitionArray* transitions = map->transitions();
     return transitions->GetTarget(number_);
   }
 
+  Map* GetTransitionTarget() {
+    return GetTransitionTarget(holder()->map());
+  }
+
   PropertyDetails GetTransitionDetails(Map* map) {
     ASSERT(IsTransition());
     TransitionArray* transitions = map->transitions();