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..e2c8c53213ec4ad772e70a7c889eefb03c2f6dcd 100644
--- a/chrome/browser/resources/md_downloads/action_service.js
+++ b/chrome/browser/resources/md_downloads/action_service.js
@@ -45,7 +45,7 @@ cr.define('downloads', function() {
      *     (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. */
@@ -80,7 +80,8 @@ cr.define('downloads', function() {
 
       // 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

     },
 
     /**