Fix GCMole warning

src/objects.cc

 // Copyright 2013 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 12213 matching lines @@
     object->ValidateElements();
     return value;
   }
   // Change elements kind from Smi-only to generic FAST if necessary.
   if (object->HasFastSmiElements() && !value->IsSmi()) {
     ElementsKind kind = object->HasFastHoleyElements()
         ? FAST_HOLEY_ELEMENTS
         : FAST_ELEMENTS;
 
     UpdateAllocationSite(object, kind);
-    object->set_map(*GetElementsTransitionMap(object, kind));
+    Handle<Map> new_map = GetElementsTransitionMap(object, kind);
+    object->set_map(*new_map);
     ASSERT(IsFastObjectElementsKind(object->GetElementsKind()));
   }
   // Increase backing store capacity if that's been decided previously.
   if (new_capacity != capacity) {
     SetFastElementsCapacitySmiMode smi_mode =
         value->IsSmi() && object->HasFastSmiElements()
             ? kAllowSmiElements
             : kDontAllowSmiElements;
     Handle<FixedArray> new_elements =
         SetFastElementsCapacityAndLength(object, new_capacity, array_length,
@@ skipping 4398 matching lines @@
 #define ERROR_MESSAGES_TEXTS(C, T) T,
   static const char* error_messages_[] = {
       ERROR_MESSAGES_LIST(ERROR_MESSAGES_TEXTS)
   };
 #undef ERROR_MESSAGES_TEXTS
   return error_messages_[reason];
 }
 
 
 } }  // namespace v8::internal