Enable use_once_callback on mojom GN rule by default

ipc/BUILD.gn

 # Copyright (c) 2012 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("//build/config/nacl/config.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//testing/test.gni")
 import("//tools/ipc_fuzzer/ipc_fuzzer.gni")
 
 component("ipc") {
@@ skipping 112 matching lines @@
   export_class_attribute = "IPC_EXPORT"
   export_define = "IPC_IMPLEMENTATION"
   export_header = "ipc/ipc_export.h"
 }
 
 mojom("test_interfaces") {
   testonly = true
   sources = [
     "ipc_test.mojom",
   ]
+
+  # TODO(crbug.com/714018): Convert the implementation to use OnceCallback.
+  use_once_callback = false
 }
 
 # This is provided as a separate target so other targets can provide param
 # traits implementations without necessarily linking to all of IPC.
 source_set("param_traits") {
   public = [
     "ipc_param_traits.h",
   ]
 }
 
@@ skipping 91 matching lines @@
       ":ipc",
     ]
     deps = [
       "//base",
       "//base/test:test_support",
       "//mojo/edk/test:test_support",
       "//testing/gtest",
     ]
   }
 }