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

chrome/browser/resources/md_downloads/action_service.js

Index: chrome/browser/resources/md_downloads/action_service.js
diff --git a/chrome/browser/resources/md_downloads/action_service.js b/chrome/browser/resources/md_downloads/action_service.js
index f984fe5a14614e3b853993e4dcaad33b70577641..d135fb3666804edb0f502f2f940e1422faf5aa0b 100644
--- a/chrome/browser/resources/md_downloads/action_service.js
+++ b/chrome/browser/resources/md_downloads/action_service.js
@@ -14,6 +14,27 @@ cr.define('downloads', function() {
   /** @constructor */
   function ActionService() {}
 
+  /**
+   * @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) {
+    /**
+     * @param {string} s
+     * @return {string} |s| without whitespace at the beginning or end.
+     */
+    function trim(s) { return s.trim(); }
+
+    /**
+     * @param {string} s
+     * @return {boolean} Whether |s| is empty.
+     */
+    function notEmpty(s) { return s.length > 0; }

[dpapad, 2015/11/25 17:50:47]

Nit: We are re-defining the trim() and notEpmty() functions every time
splitTerms() is called. How about moving the outside of splitTerms (but still
within the cr.definde('downloads', function() {...}).

[Dan Beam, 2015/11/25 20:23:23]

Done.

+
+    // Split quoted terms (e.g., 'The "lazy" dog' => ['The', 'lazy', 'dog']).
+    return searchText.split(/"([^"]*)"/).map(trim).filter(notEmpty);
+  };
+
   ActionService.prototype = {
     /** @param {string} id ID of the download to cancel. */
     cancel: chromeSendWithId('cancel'),
@@ -45,7 +66,7 @@ cr.define('downloads', function() {
      *     (i.e. has a non-empty search term).
      */
     isSearching: function() {
-      return this.searchText_.length > 0;
+      return !!this.searchText_;

[dpapad, 2015/11/25 17:50:47]

If you follow the comment above, then you can re-use the notEmpty() here, as
notEmpty(this.searchText_);

[Dan Beam, 2015/11/25 20:23:23]

changed a little, but basically doing this

     },
 
     /** Opens the current local destination for downloads. */
@@ -77,10 +98,7 @@ cr.define('downloads', function() {
         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));
+      chrome.send('getDownloads', ActionService.splitTerms(searchText));
     },
 
     /**