Add progress bars to MD downloads.

chrome/browser/resources/md_downloads/item_view.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() {
   var ItemView = Polymer({
     is: 'item-view',
 
     /** @param {!downloads.ThrottledIconLoader} iconLoader */
     factoryImpl: function(iconLoader) {
@@ skipping 98 matching lines @@
           link.setAttribute('column-type', 'controlled-by');
           link.textContent = data.by_ext_name;
         }
 
         this.ensureTextIs_(this.$['src-url'], data.url);
         this.$['src-url'].href = data.url;
         this.ensureTextIs_(this.$.status, this.getStatusText_(data));
 
         this.$.progress.hidden = !isInProgress;
 
-        // TODO(dbeam): implement progress.
+        if (isInProgress)
+          this.$.progress.value = data.percent;
       }
     },
 
     /**
      * Overwrite |el|'s textContent if it differs from |text|.
      * @param {!Element} el
      * @param {string} text
      * @private
      */
     ensureTextIs_: function(el, text) {
@@ skipping 111 matching lines @@
     },
 
     /** @private */
     onDiscardClick_: function() {
       chrome.send('discardDangerous', [this.id_]);
     },
   });
 
   return {ItemView: ItemView};
 });