Fix array concat to follow the specification in the presence of element getters.

src/objects-inl.h

 // Copyright 2010 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 751 matching lines @@
   return Failure::Exception();
 }
 
 
 bool Object::HasSpecificClassOf(String* name) {
   return this->IsJSObject() && (JSObject::cast(this)->class_name() == name);
 }
 
 
 MaybeObject* Object::GetElement(uint32_t index) {
+  // GetElement can trigger a getter which can cause allocation.
+  // This was not always the case. This ASSERT is here to catch
+  // leftover incorrect uses.
+  ASSERT(Heap::IsAllocationAllowed());
   return GetElementWithReceiver(this, index);
 }
 
 
 Object* Object::GetElementNoExceptionThrown(uint32_t index) {
   MaybeObject* maybe = GetElementWithReceiver(this, index);
   ASSERT(!maybe->IsFailure());
   Object* result = NULL;  // Initialization to please compiler.
   maybe->ToObject(&result);
   return result;
@@ skipping 3149 matching lines @@
 #undef WRITE_INT_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_