Use Object.observe() instead of Polyfills

ui/file_manager/audio_player/js/audio_player_model.js

 // Copyright 2014 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.
 
 (function(global) {
   'use strict';
 
   /**
    * List of values to be stored into the model.
    * @type {Object<string, *>}
@@ skipping 36 matching lines @@
                           map(function(a) {
                             return STORAGE_PREFIX + a;
                           });
 
     chrome.storage.local.get(objectsToBeRead, function(result) {
       for (var key in result) {
         // Strips the prefix.
         model[key.substr(STORAGE_PREFIX.length)] = result[key];
       }
       callback();
-    }.bind(this));
+    });
   };
 
   /**
    * The model class for audio player.
    * @constructor
    */
   function AudioPlayerModel() {
     // Initializes values.
     for (var key in VALUES) {
       this[key] = VALUES[key];
     }
     Object.seal(this);
 
     // Restores the values from the storage
-    loadModel(this, function() {
+    var target = this;
+    loadModel(target, function() {
       // Installs observer to watch changes of the values.
-      var observer = new ObjectObserver(this);
-      observer.open(function(added, removed, changed, getOldValueFn) {
-        saveModel(this);
-      }.bind(this));
-    }.bind(this));
+      Object.observe(target, function(changes) {
+        saveModel(target);
+      });
+    });
   }
 
   // Exports AudioPlayerModel class to the global.
   global.AudioPlayerModel = AudioPlayerModel;
 
 })(this || window);