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

chrome/test/data/webui/md_downloads/layout_tests.js

Index: chrome/test/data/webui/md_downloads/layout_tests.js
diff --git a/chrome/test/data/webui/md_downloads/layout_tests.js b/chrome/test/data/webui/md_downloads/layout_tests.js
index 7c09cf6ffb0950f1a228c5b4cf105ef7a2934783..d7f769db0e96165f1a2de6ff7933fe4d9ad51bb1 100644
--- a/chrome/test/data/webui/md_downloads/layout_tests.js
+++ b/chrome/test/data/webui/md_downloads/layout_tests.js
@@ -15,10 +15,10 @@ cr.define('downloads.layout_tests', function() {
       });
 
       test('long URLs ellide', function() {
-        manager.updateAll_([{
+        manager.insertItems_(0, [{

[dpapad, 2015/11/24 18:42:33]

Nit: Can you avoid referring to private method by using Manager.insertItems()
instead? This way you also test the method that is actually called by the C++
side.

[Dan Beam, 2015/11/25 04:06:37]

Done.

           file_name: 'file name',
           state: downloads.States.COMPLETE,
-          url: 'a'.repeat(10000),
+          url: 'a'.repeat(1000),
         }]);
 
         Polymer.dom.flush();