MD Settings: About page, updating buttons based on current update status.

chrome/browser/resources/settings/about_page/about_page_browser_proxy.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.
 
 /**
  * @fileoverview A helper object used from the "About" section to interact with
  * the browser.
  */
 
 <if expr="chromeos">
@@ skipping 36 matching lines @@
   NEARLY_UPDATED: 'nearly_updated',
   UPDATED: 'updated',
   FAILED: 'failed',
   DISABLED: 'disabled',
   DISABLED_BY_ADMIN: 'disabled_by_admin',
 };
 
 /**
  * @typedef {{
  *   status: !UpdateStatus,
- *   progress: number,
- *   message: string,
+ *   progress: (number|undefined),

[tommycli, 2016/05/20 22:53:18]

Looking at the C++ handler, these are always defined right?

Is this only to accommodate the test code? Maybe not worth.

[dpapad, 2016/05/20 23:25:35]

Test code but also prod code (see about_page.js where onUpdateStatusChanged_ is
called manually once). But also I think this is better reflecting that "message"
is only meaningful sometimes. Otherwise this fact is very implicit and the
developer is surprised by seeing empty strings in most cases. Ideally I would
change the C++ to only pass it when it is non-empty, but I consider the priority
of this little cleanup lower than getting the about page to a functional state.

+ *   message: (string|undefined),
  * }}
  */
 var UpdateStatusChangedEvent;
 
 cr.define('settings', function() {
   /**
    * @param {!BrowserChannel} channel
    * @return {string}
    */
   function browserChannelToI18nId(channel) {
@@ skipping 129 matching lines @@
     }
 </if>
   };
 
   return {
     AboutPageBrowserProxy: AboutPageBrowserProxy,
     AboutPageBrowserProxyImpl: AboutPageBrowserProxyImpl,
     browserChannelToI18nId: browserChannelToI18nId,
   };
 });