Fix bug in Object.defineProperty where a growing lements dictionary was ignored.

src/runtime.cc

 // Copyright 2011 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 3896 matching lines @@
       // If proxy is detached, ignore the assignment. Alternatively,
       // we could throw an exception.
       if (proto->IsNull()) return *obj_value;
       js_object = Handle<JSObject>::cast(proto);
     }
     NormalizeElements(js_object);
     Handle<NumberDictionary> dictionary(js_object->element_dictionary());
     // Make sure that we never go back to fast case.
     dictionary->set_requires_slow_elements();
     PropertyDetails details = PropertyDetails(attr, NORMAL);
-    NumberDictionarySet(dictionary, index, obj_value, details);
+    Handle<NumberDictionary> extended_dictionary =
+        NumberDictionarySet(dictionary, index, obj_value, details);
+    if (*extended_dictionary != *dictionary) {
+      js_object->set_elements(*extended_dictionary);
+    }
     return *obj_value;
   }
 
   LookupResult result;
   js_object->LookupRealNamedProperty(*name, &result);
 
   // To be compatible with safari we do not change the value on API objects
   // in defineProperty. Firefox disagrees here, and actually changes the value.
   if (result.IsProperty() &&
       (result.type() == CALLBACKS) &&
@@ skipping 8424 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(false);
   }
 }
 
 
 } }  // namespace v8::internal