AudioPlayer: Stop using Object.observe() and Array.observe().

ui/file_manager/audio_player/elements/track_list.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.
 
 /**
  * @typedef {?{
  *   url: string,
  *   title: string,
  *   artist: string,
  *   artwork: Object,
@@ skipping 38 matching lines @@
         value: false,
         observer: 'shuffleChanged'
       }
     },
 
     /**
      * Initializes an element. This method is called automatically when the
      * element is ready.
      */
     ready: function() {
-      this.observeTrackList();
-
       window.addEventListener('resize', this.onWindowResize_.bind(this));
     },
 
-    observeTrackList: function() {
-      // Unobserve the previous track list.
-      if (this.unobserveTrackList_)
-        this.unobserveTrackList_();
-
-      // Observe the new track list.
-      var observer = this.tracksValueChanged_.bind(this);
-      Array.observe(this.tracks, observer);
-
-      // Set the function to unobserve it.
-      this.unobserveTrackList_ = function(tracks, observer) {
-        Array.unobserve(tracks, observer);
-      }.bind(null, this.tracks, observer);
-    },
-
     /**
      * Play order of the tracks. Each value is the index of 'this.tracks'.
      * @type {Array<number>}
      */
     playOrder: [],
 
     /**
      * Invoked when 'shuffle' property is changed.
      * @param {boolean} newValue New value.
      * @param {boolean} oldValue Old value.
@@ skipping 34 matching lines @@
 
     /**
      * Invoked when 'tracks' property is changed.
      * @param {Array<!TrackInfo>} newValue New value.
      * @param {Array<!TrackInfo>} oldValue Old value.
      */
     tracksChanged: function(newValue, oldValue) {
       // Note: Sometimes both oldValue and newValue are null though the actual
       // values are not null. Maybe it's a bug of Polymer.
 
-      // Re-register the observer of 'this.tracks'.
-      this.observeTrackList();
-
       if (this.tracks.length !== 0) {
         // Restore the active track.
         if (this.currentTrackIndex !== -1 &&
             this.currentTrackIndex < this.tracks.length) {
           this.set('tracks.' + this.currentTrackIndex + '.active', true);
         }
 
         // Reset play order and current index.
         this.generatePlayOrder(false /* no need to keep the current track */);
       } else {
         this.playOrder = [];
         this.currentTrackIndex = -1;
       }
     },
 
     /**
-     * Invoked when the value in the 'tracks' is changed.
-     * @param {Array<Object>} changes The detail of the change.
-     */
-    tracksValueChanged_: function(changes) {
-      if (this.tracks.length === 0)
-        this.currentTrackIndex = -1;
-      else
-        this.set('tracks.' + this.currentTrackIndex + '.active', true);
-    },
-
-    /**
      * Invoked when the track element is clicked.
      * @param {Event} event Click event.
      */
     trackClicked: function(event) {
       var index = ~~event.currentTarget.getAttribute('index');
       var track = this.tracks[index];
       if (track) {
         if (event.target.classList.contains('icon')) {
           // If the play icon on the track is clicked, change the current track
           // and start playing it regardless of current play state.
@@ skipping 155 matching lines @@
 
       var newTrackIndex = this.playOrder[newPlayOrder];
       console.assert(
           (0 <= newTrackIndex && newTrackIndex < this.tracks.length),
           'Insufficient TrackList.playOrder. New Play Order: ' + newPlayOrder);
 
       return newTrackIndex;
     },
   });
 })();  // Anonymous closure