Enable use_once_callback on mojom GN rule by default

mojo/common/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//testing/test.gni")
 
 group("common") {
   public_deps = [
     ":common_base",
@@ skipping 35 matching lines @@
 }
 
 mojom("test_common_custom_types") {
   sources = [
     "test_common_custom_types.mojom",
     "traits_test_service.mojom",
   ]
   public_deps = [
     ":common_custom_types",
   ]
+
+  # TODO(crbug.com/714018): Convert the implementation to use OnceCallback.
+  use_once_callback = false
 }
 
 test("mojo_common_unittests") {
   deps = [
     ":common",
     ":common_custom_types",
     ":struct_traits",
     ":test_common_custom_types",
     "//base",
     "//base:message_loop_tests",
@@ skipping 19 matching lines @@
   ]
   deps = [
     ":common_custom_types_shared_cpp_sources",
     "//base:base",
     "//mojo/public/cpp/system",
   ]
   public_deps = [
     "//base:i18n",
   ]
 }