MD Downloads: track downloads in C++, dispatch discrete JS updates

chrome/browser/resources/md_downloads/action_service.js

 // Copyright 2015 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.
 
 cr.define('downloads', function() {
   /**
    * @param {string} chromeSendName
    * @return {function(string):void} A chrome.send() callback with curried name.
    */
   function chromeSendWithId(chromeSendName) {
@@ skipping 27 matching lines @@
     },
 
     /** @param {string} id ID of the download that the user started dragging. */
     drag: chromeSendWithId('drag'),
 
     /**
      * @return {boolean} Whether the user is currently searching for downloads
      *     (i.e. has a non-empty search term).
      */
     isSearching: function() {
-      return this.searchText_.length > 0;
+      return (this.searchText_ || '').length > 0;
     },
 
     /** Opens the current local destination for downloads. */
     openDownloadsFolder: chrome.send.bind(chrome, 'openDownloadsFolder'),
 
     /**
      * @param {string} id ID of the download to run locally on the user's box.
      */
     openFile: chromeSendWithId('openFile'),
 
@@ skipping 13 matching lines @@
     saveDangerous: chromeSendWithId('saveDangerous'),
 
     /** @param {string} searchText What to search for. */
     search: function(searchText) {
       if (this.searchText_ == searchText)
         return;
 
       this.searchText_ = searchText;
 
       // Split quoted terms (e.g., 'The "lazy" dog' => ['The', 'lazy', 'dog']).
       function trim(s) { return s.trim(); }

[dpapad, 2015/11/20 21:55:15]

Nit: Add @param, @return?

[Dan Beam, 2015/11/21 01:40:42]

Done.

-      chrome.send('getDownloads', searchText.split(/"([^"]*)"/).map(trim));
+      chrome.send('getDownloads',
+          searchText ? searchText.split(/"([^"]*)"/).map(trim) : []);

[dpapad, 2015/11/20 21:55:15]

Nit: Use isSearching instead of implicit conversion to boolean?

chrome.send('getDownloads',
    this.isSearching() ? searchText.split(/"([^"]*)"/).map(trim) : []);

[Dan Beam, 2015/11/21 01:40:42]

ehhhhhhhhh

     },
 
     /**
      * Shows the local folder a finished download resides in.
      * @param {string} id ID of the download to show.
      */
     show: chromeSendWithId('show'),
 
     /** Undo download removal. */
     undo: chrome.send.bind(chrome, 'undo'),
   };
 
   cr.addSingletonGetter(ActionService);
 
   return {ActionService: ActionService};
 });