rv = EndMediaChange(); return rv;
mMedia = new DOMMediaListImpl(tmp, this); NS_ENSURE_TRUE(mMedia, NS_ERROR_OUT_OF_MEMORY);  NS_ADDREF(mMedia); }  if (mMedia) { mMedia->AppendElement(aMedium); } return result;
DOMMediaListImpl::AppendMedium(const nsAString& aNewMedium){  nsresult rv;  rv = BeginMediaChange();  if (NS_FAILED(rv))    return rv;    rv = Append(aNewMedium);  if (NS_FAILED(rv))    return rv;  rv = EndMediaChange();  return rv;}