[AudioPlayer] Don't start a playback automatically when reopening

chrome/browser/resources/file_manager/audio_player/elements/audio_player.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.
 
 'use strict';
 
 Polymer('audio-player', {
   /**
    * Child Elements
    */
   audioController: null,
   audioElement: null,
   trackList: null,
 
-  // Attributes of the element (little charactor only)
+  // Attributes of the element (little charactor only).
+  // These value must be used only to data binding and shouldn't be assignred
+  // anu value nowhere except in the handler.
   playing: false,
   currenttrackurl: '',
 
   /**
    * Model object of the Audio Player.
    * @type {AudioPlayerModel}
    */
   model: null,
 
   /**
@@ skipping 37 matching lines @@
    * @param {number} newValue new value.
    */
   onCurrentTrackIndexChanged: function(oldValue, newValue) {
     var currentTrackUrl = '';
 
     if (oldValue != newValue) {
       var currentTrack = this.trackList.getCurrentTrack();
       if (currentTrack && currentTrack.url != this.audioElement.src) {
         this.audioElement.src = currentTrack.url;
         currentTrackUrl = this.audioElement.src;
-        this.audioElement.play();
+        if (this.audioController.playing)
+          this.audioElement.play();
       }
     }
 
     // The attributes may be being watched, so we change it at the last.
     this.currenttrackurl = currentTrackUrl;
   },
 
   /**
    * Invoked when audioController.playing is changed.
    * @param {boolean} oldValue old value.
@@ skipping 12 matching lines @@
 
       if (this.audioElement.src) {
         this.currenttrackurl = this.audioElement.src;
         this.audioElement.play();
         return;
       }
     }
 
     // When the new status is "stopped".
     this.cancelAutoAdvance_();
-    this.audioController.playing = false;
     this.audioElement.pause();
     this.currenttrackurl = '';
     this.lastAudioUpdateTime_ = null;
   },
 
   /**
    * Invoked when audioController.volume is changed.
    * @param {number} oldValue old value.
    * @param {number} newValue new value.
    */
@@ skipping 78 matching lines @@
    * @param {boolean} repeat True if repeat-mode is enabled. False otherwise.
    * @private
    */
   advance_: function(forward, repeat) {
     this.cancelAutoAdvance_();
 
     var nextTrackIndex = this.trackList.getNextTrackIndex(forward, true);
     var isNextTrackAvailable =
         (this.trackList.getNextTrackIndex(forward, repeat) !== -1);
 
+    this.audioController.playing = isNextTrackAvailable;
     this.trackList.currentTrackIndex = nextTrackIndex;
 
-    if (isNextTrackAvailable) {
-      var nextTrack = this.trackList.tracks[nextTrackIndex];
-      this.audioElement.src = nextTrack.url;
-      this.audioElement.play();
-    } else {
-      this.audioElement.pause();
-    }
+    Platform.performMicrotaskCheckpoint();
   },
 
   /**
    * Timeout ID of auto advance. Used internally in scheduleAutoAdvance_() and
    *     cancelAutoAdvance_().
    * @type {number}
    * @private
    */
   autoAdvanceTimer_: null,
 
@@ skipping 65 matching lines @@
     }
   },
 
   /**
    * Invoked when the audio player is being unloaded.
    */
   onPageUnload: function() {
     this.audioElement.src = '';  // Hack to prevent crashing.
   },
 });