Support new-style Mojo JS core API on IOS.

ios/web/webui/resources/sync_message_channel.js

-// 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 "ios/mojo/public/js/sync_message_channel"
-//
-// This module provides the synchronous communication channel between
-// JavaScript and native code, which serves as mojo backend.
-
-define("ios/mojo/public/js/sync_message_channel", [], function() {
-  var exports = {};
-
-  /**
-   * Synchronously sends a message to mojo backend.
-   * @param {!Object} message to send.
-   * @return {Object} Response from mojo backend.
-   */
-  exports.sendMessage = function(message) {
-    var response = window.prompt(__gCrWeb.common.JSONStringify(message));
-    return response ? JSON.parse(response) : undefined;
-  }
-
-  return exports;
-});