ash: Use mojo LocaleNotificationController interface.

ash/public/interfaces/locale.mojom

+// Copyright 2016 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.
+
+module ash.mojom;
+
+// Sent as the response to LocaleNotificationController.OnLocaleChanged().
+enum LocaleNotificationResult {
+  ACCEPT,
+  REVERT
+};
+
+// Used by Chrome to make ash show a notification.
+interface LocaleNotificationController {
+  // Displays a notification in ash prompting the user whether to accept a
+  // change in the locale. If the user clicks the accept button (or closes the
+  // notification), OnLocaleChange() returns ACCEPT. If the user clicks the
+  // revert button, returns REVERT.
+  OnLocaleChanged(string current, string from, string to)
+      => (LocaleNotificationResult result);
+};