Add an update warning for downloading over mobile data

chrome/browser/resources/settings/about_page/update_warning_dialog.js

 // Copyright 2017 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.
 
 /**
  * @fileoverview 'settings-update-warning-dialog' is a component warning the
  * user about update over mobile data. By clicking 'Continue', the user
  * agrees to download update using mobile data.
  */
 Polymer({
   is: 'settings-update-warning-dialog',
 
   behaviors: [I18nBehavior],
 
+  /** @private {?settings.AboutPageBrowserProxy} */
+  browserProxy_: null,
+
   /** @override */
   ready: function() {
     this.browserProxy_ = settings.AboutPageBrowserProxyImpl.getInstance();
   },
 
   /** @override */
   attached: function() {
     this.$.dialog.showModal();
   },
 
   /** @private */
   onCancelTap_: function() {
-    // TODO(weidongg): implement the real behaviors here.
     this.$.dialog.close();
   },
 
   /** @private */
   onContinueTap_: function() {
-    // TODO(weidongg): implement the real behaviors here.
+    this.browserProxy_.requestUpdateOverCellular(this.target_version,
+                                                 this.target_size);
     this.$.dialog.close();
   },
 
   /**
-   * @param {string} updateSizeMb Size of the update in megabytes.
+   * @param {string} updateSize Size of the update in bytes.
    * @private
    */
-  setUpdateWarningMessage: function(updateSizeMb) {
-     this.$$("#update-warning-message").innerHTML =
-         this.i18n("aboutUpdateWarningMessage", updateSizeMb);
+  setUpdateWarningMessage: function(version, size) {
+    this.target_version = version;
+    this.target_size = size;
+    this.$$("#update-warning-message").innerHTML =
+        this.i18n("aboutUpdateWarningMessage",
+                  // Convert bytes to megabytes
+                  Math.floor(Number(size) / (1024 * 1024)));
   },
 });