DescriptorArray::CopyFrom should always drop transitions for CALLBACKS.

src/bootstrapper.cc

 // 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 1725 matching lines @@
 
     // Update map with length accessor from Array and add "index" and "input".
     Handle<DescriptorArray> reresult_descriptors =
         factory()->NewDescriptorArray(3);
     DescriptorArray::WhitenessWitness witness(*reresult_descriptors);
 
     JSFunction* array_function = global_context()->array_function();
     Handle<DescriptorArray> array_descriptors(
         array_function->initial_map()->instance_descriptors());
     int index = array_descriptors->SearchWithCache(heap()->length_symbol());
-    reresult_descriptors->CopyFrom(0, *array_descriptors, index, witness);
+    MaybeObject* copy_result =
+        reresult_descriptors->CopyFrom(0, *array_descriptors, index, witness);
+    if (copy_result->IsFailure()) return false;
 
     int enum_index = 0;
     {
       FieldDescriptor index_field(heap()->index_symbol(),
                                   JSRegExpResult::kIndexIndex,
                                   NONE,
                                   enum_index++);
       reresult_descriptors->Set(1, &index_field, witness);
     }
 
@@ skipping 605 matching lines @@
   return from + sizeof(NestingCounterType);
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   ASSERT(!IsActive());
 }
 
 } }  // namespace v8::internal