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) {
     return function(id) { chrome.send(chromeSendName, [id]); };
   }
 
   /** @constructor */
   function ActionService() {}
 
+  /**
+   * @param {string} s
+   * @return {string} |s| without whitespace at the beginning or end.
+   */
+  function trim(s) { return s.trim(); }
+
+  /**
+   * @param {string|undefined} value
+   * @return {boolean} Whether |value| is truthy.
+   */
+  function truthy(value) { return !!value; }
+
+  /**
+   * @param {string} searchText Input typed by the user into a search box.
+   * @return {Array<string>} A list of terms extracted from |searchText|.
+   */
+  ActionService.splitTerms = function(searchText) {
+    // Split quoted terms (e.g., 'The "lazy" dog' => ['The', 'lazy', 'dog']).
+    return searchText.split(/"([^"]*)"/).map(trim).filter(truthy);
+  };
+
   ActionService.prototype = {
     /** @param {string} id ID of the download to cancel. */
     cancel: chromeSendWithId('cancel'),
 
     /** Instructs the browser to clear all finished downloads. */
     clearAll: function() {
       if (loadTimeData.getBoolean('allowDeletingHistory')) {
         chrome.send('clearAll');
         this.search('');
       }
     },
 
     /** @param {string} id ID of the dangerous download to discard. */
     discardDangerous: chromeSendWithId('discardDangerous'),
 
     /** @param {string} url URL of a file to download. */
     download: function(url) {
       var a = document.createElement('a');
       a.href = url;
       a.setAttribute('download', '');
       a.click();
     },
 
     /** @param {string} id ID of the download that the user started dragging. */
     drag: chromeSendWithId('drag'),
 
+    /** @private {boolean} */
+    isSearching_: false,
+
     /**
      * @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.isSearching_;
     },
 
     /** 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 12 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(); }
-      chrome.send('getDownloads', searchText.split(/"([^"]*)"/).map(trim));
+      var terms = ActionService.splitTerms(searchText);
+      this.isSearching_ = terms.length > 0;
+
+      chrome.send('getDownloads', terms);
     },
 
     /**
      * 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};
 });