ui/file_manager/audio_player/elements/audio_player.js - chromium/src - Git at Google

 // 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.

 Polymer({
   is: 'audio-player',

   listeners: {
     'toggle-pause-event': 'onTogglePauseEvent_',
     'small-forward-skip-event': 'onSmallForwardSkipEvent_',
     'small-backword-skip-event': 'onSmallBackwordSkipEvent_',
     'big-forward-skip-event': 'onBigForwardSkipEvent_',
     'big-backword-skip-event': 'onBigBackwordSkipEvent_',
   },

   properties: {
     /**
      * Flag whether the audio is playing or paused. True if playing, or false
      * paused.
      */
     playing: {
       type: Boolean,
       observer: 'playingChanged',
       reflectToAttribute: true
     },

     /**
      * Current elapsed time in the current music in millisecond.
      */
     time: {
       type: Number,
       observer: 'timeChanged'
     },

     /**
      * Whether the shuffle button is ON.
      */
     shuffle: {
       type: Boolean,
       notify: true
     },

     /**
      * Whether the repeat button is ON.
      */
     repeat: {
       type: Boolean,
       notify: true
     },

     /**
      * The audio volume. 0 is silent, and 100 is maximum loud.
      */
     volume: {
       type: Number,
       notify: true
     },

     /**
      * Whether the playlist is expanded or not.
      */
     playlistExpanded: {
       type: Boolean,
       notify: true
     },
     /**
      * Whether the artwork is expanded or not.
      */
     trackInfoExpanded: {
       type: Boolean,
       notify: true
     },

     /**
      * Track index of the current track.
      */
     currentTrackIndex: {
       type: Number,
       observer: 'currentTrackIndexChanged'
     },

     /**
      * URL of the current track. (exposed publicly for tests)
      */
     currenttrackurl: {
       type: String,
       value: '',
       reflectToAttribute: true
     },

     /**
      * The number of played tracks. (exposed publicly for tests)
      */
     playcount: {
       type: Number,
       value: 0,
       reflectToAttribute: true
     },

     ariaLabels: {
       type: Object
     }
   },

   /**
    * The last playing state when user starts dragging the seek bar.
    * @private {boolean}
    */
   wasPlayingOnDragStart_: false,

   /**
    * Initializes an element. This method is called automatically when the
    * element is ready.
    */
   ready: function() {
     this.addEventListener('keydown', this.onKeyDown_.bind(this));

     this.$.audioController.addEventListener('dragging-changed',
         this.onDraggingChanged_.bind(this));

     this.$.audio.addEventListener('ended', this.onAudioEnded.bind(this));
     this.$.audio.addEventListener('error', this.onAudioError.bind(this));

     var onAudioStatusUpdatedBound = this.onAudioStatusUpdate_.bind(this);
     this.$.audio.addEventListener('timeupdate', onAudioStatusUpdatedBound);
     this.$.audio.addEventListener('ended', onAudioStatusUpdatedBound);
     this.$.audio.addEventListener('play', onAudioStatusUpdatedBound);
     this.$.audio.addEventListener('pause', onAudioStatusUpdatedBound);
     this.$.audio.addEventListener('suspend', onAudioStatusUpdatedBound);
     this.$.audio.addEventListener('abort', onAudioStatusUpdatedBound);
     this.$.audio.addEventListener('error', onAudioStatusUpdatedBound);
     this.$.audio.addEventListener('emptied', onAudioStatusUpdatedBound);
     this.$.audio.addEventListener('stalled', onAudioStatusUpdatedBound);
   },

   /**
    * Invoked when trackList.currentTrackIndex is changed.
    * @param {number} newValue new value.
    * @param {number} oldValue old value.
    */
   currentTrackIndexChanged: function(newValue, oldValue) {
     var currentTrackUrl = '';

     if (oldValue != newValue) {
       var currentTrack = this.$.trackList.getCurrentTrack();
       if(currentTrack && currentTrack != this.$.trackInfo.track){
         this.$.trackInfo.track = currentTrack;
         this.$.trackInfo.artworkAvailable = !!currentTrack.artworkUrl;
       }
       if (currentTrack && currentTrack.url != this.$.audio.src) {
         this.$.audio.src = currentTrack.url;
         currentTrackUrl = this.$.audio.src;
         if (this.playing)
           this.$.audio.play();
       }
     }

     // The attributes may be being watched, so we change it at the last.
     this.currenttrackurl = currentTrackUrl;
   },

   /**
    * Invoked when playing is changed.
    * @param {boolean} newValue new value.
    * @param {boolean} oldValue old value.
    */
   playingChanged: function(newValue, oldValue) {
     if (newValue) {
       if (!this.$.audio.src) {
         var currentTrack = this.$.trackList.getCurrentTrack();
         if (currentTrack && currentTrack.url != this.$.audio.src) {
           this.$.audio.src = currentTrack.url;
         }
       }

       if (this.$.audio.src) {
         this.currenttrackurl = this.$.audio.src;
         this.$.audio.play();
         return;
       }
     }

     // When the new status is "stopped".
     this.cancelAutoAdvance_();
     this.$.audio.pause();
     this.currenttrackurl = '';
     this.lastAudioUpdateTime_ = null;
   },

   /**
    * Invoked when time is changed.
    * @param {number} newValue new time (in ms).
    * @param {number} oldValue old time (in ms).
    */
   timeChanged: function(newValue, oldValue) {
     // Ignores updates from the audio element.
     if (this.lastAudioUpdateTime_ === newValue)
       return;

     if (this.$.audio.readyState !== 0)
       this.$.audio.currentTime = this.time / 1000;
   },

   /**
    * Invoked when the next button in the controller is clicked.
    * This handler is registered in the 'on-click' attribute of the element.
    */
   onControllerNextClicked: function() {
     this.advance_(true /* forward */, true /* repeat */);
   },

   /**
    * Invoked when the previous button in the controller is clicked.
    * This handler is registered in the 'on-click' attribute of the element.
    */
   onControllerPreviousClicked: function() {
     this.advance_(false /* forward */, true /* repeat */);
   },

   /**
    * Invoked when the playback in the audio element is ended.
    * This handler is registered in this.ready().
    */
   onAudioEnded: function() {
     this.playcount++;
     this.advance_(true /* forward */, this.repeat);
   },

   /**
    * Invoked when the playback in the audio element gets error.
    * This handler is registered in this.ready().
    */
   onAudioError: function() {
     this.scheduleAutoAdvance_(true /* forward */, this.repeat);
   },

   /**
    * Invoked when the time of playback in the audio element is updated.
    * This handler is registered in this.ready().
    * @private
    */
   onAudioStatusUpdate_: function() {
     this.time = (this.lastAudioUpdateTime_ = this.$.audio.currentTime * 1000);
     this.duration = this.$.audio.duration * 1000;
     this.playing = !this.$.audio.paused;
   },

   /**
    * Invoked when receivig a request to start playing the current music.
    */
   onPlayCurrentTrack: function() {
     this.$.audio.play();
   },

   /**
    * Invoked when receiving a request to replay the current music from the track
    * list element.
    */
   onReplayCurrentTrack: function() {
     // Changes the current time back to the beginning, regardless of the current
     // status (playing or paused).
     this.$.audio.currentTime = 0;
     this.time = 0;
     this.$.audio.play();
   },

   /**
    * Goes to the previous or the next track.
    * @param {boolean} forward True if next, false if previous.
    * @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.playing = isNextTrackAvailable;

     var shouldFireEvent = this.$.trackList.currentTrackIndex === nextTrackIndex;
     this.$.trackList.currentTrackIndex = nextTrackIndex;
     this.$.audio.currentTime = 0;
     // If the next track and current track is the same,
     // the event will not be fired.
     // So we will fire the event here.
     // This happenes if there is only one song.
     if (shouldFireEvent) {
       this.$.trackList.fire('current-track-index-changed');
     }
   },

   /**
    * Timeout ID of auto advance. Used internally in scheduleAutoAdvance_() and
    *     cancelAutoAdvance_().
    * @type {number?}
    * @private
    */
   autoAdvanceTimer_: null,

   /**
    * Schedules automatic advance to the next track after a timeout.
    * @param {boolean} forward True if next, false if previous.
    * @param {boolean} repeat True if repeat-mode is enabled. False otherwise.
    * @private
    */
   scheduleAutoAdvance_: function(forward, repeat) {
     this.cancelAutoAdvance_();
     var currentTrackIndex = this.currentTrackIndex;

     var timerId = setTimeout(
         function() {
           // If the other timer is scheduled, do nothing.
           if (this.autoAdvanceTimer_ !== timerId)
             return;

           this.autoAdvanceTimer_ = null;

           // If the track has been changed since the advance was scheduled, do
           // nothing.
           if (this.currentTrackIndex !== currentTrackIndex)
             return;

           // We are advancing only if the next track is not known to be invalid.
           // This prevents an endless auto-advancing in the case when all tracks
           // are invalid (we will only visit each track once).
           this.advance_(forward, repeat);
         }.bind(this),
         3000);

     this.autoAdvanceTimer_ = timerId;
   },

   /**
    * Cancels the scheduled auto advance.
    * @private
    */
   cancelAutoAdvance_: function() {
     if (this.autoAdvanceTimer_) {
       clearTimeout(this.autoAdvanceTimer_);
       this.autoAdvanceTimer_ = null;
     }
   },

   /**
    * The list of the tracks in the playlist.
    *
    * When it changed, current operation including playback is stopped and
    * restarts playback with new tracks if necessary.
    *
    * @type {Array<TrackInfo>}
    */
   get tracks() {
     return this.$.trackList ? this.$.trackList.tracks : null;
   },
   set tracks(tracks) {
     if (this.$.trackList.tracks === tracks)
       return;

     this.cancelAutoAdvance_();

     this.$.trackList.tracks = tracks;
     var currentTrack = this.$.trackList.getCurrentTrack();
     if (currentTrack && currentTrack.url != this.$.audio.src) {
       this.$.audio.src = currentTrack.url;
       this.$.audio.play();
     }
   },

   /**
    * Notifis the track-list element that the metadata for specified track is
    * updated.
    * @param {number} index The index of the track whose metadata is updated.
    */
   notifyTrackMetadataUpdated: function(index) {
     if (index < 0 || index >= this.tracks.length)
       return;

     this.$.trackList.notifyPath('tracks.' + index + '.title',
         this.tracks[index].title);
     this.$.trackList.notifyPath('tracks.' + index + '.artist',
         this.tracks[index].artist);

     if (this.$.trackInfo.track &&
         this.$.trackInfo.track.url === this.tracks[index].url){
       this.$.trackInfo.notifyPath('track.title', this.tracks[index].title);
       this.$.trackInfo.notifyPath('track.artist', this.tracks[index].artist);
       var artworkUrl = this.tracks[index].artworkUrl;
       if (artworkUrl) {
         this.$.trackInfo.notifyPath('track.artworkUrl',
             this.tracks[index].artworkUrl);
         this.$.trackInfo.artworkAvailable = true;
       } else {
         this.$.trackInfo.notifyPath('track.artworkUrl', undefined);
         this.$.trackInfo.artworkAvailable = false;
       }
     }
   },

   /**
    * Invoked when the audio player is being unloaded.
    */
   onPageUnload: function() {
     this.$.audio.src = '';  // Hack to prevent crashing.
   },

   /**
    * Invoked when dragging state of seek bar on control panel is changed.
    * During the user is dragging it, audio playback is paused temporalily.
    */
   onDraggingChanged_: function() {
     if (this.$.audioController.dragging) {
       if (this.playing) {
         this.wasPlayingOnDragStart_ = true;
         this.$.audio.pause();
       }
     } else {
       if (this.wasPlayingOnDragStart_) {
         this.$.audio.play();
         this.wasPlayingOnDragStart_ = false;
       }
     }
   },

   /**
    * Invoked when the 'keydown' event is fired.
    * @param {Event} event The event object.
    */
   onKeyDown_: function(event) {
     switch (event.key) {
       case 'MediaTrackNext':
         this.onControllerNextClicked();
         break;
       case 'MediaPlayPause':
         this.playing = !this.playing;
         break;
       case 'MediaTrackPrevious':
         this.onControllerPreviousClicked();
         break;
       case 'MediaStop':
         // TODO: Define "Stop" behavior.
         break;
     }
   },

   /**
    * Computes volume value for audio element. (should be in [0.0, 1.0])
    * @param {number} volume Volume which is set in the UI. ([0, 100])
    * @return {number}
    */
   computeAudioVolume_: function(volume) {
     return volume / 100;
   },

   /**
    * Toggle pause.
    * @private
    */
   onTogglePauseEvent_: function(event) {
     this.$.audioController.playClick();
   },

   /**
    * Small skip forward.
    * @private
    */
   onSmallForwardSkipEvent_: function(event) {
     this.$.audioController.smallSkip(true);
   },

   /**
    * Small skip backword.
    * @private
    */
   onSmallBackwordSkipEvent_: function(event) {
     this.$.audioController.smallSkip(false);
   },

   /**
    * Big skip forward.
    * @private
    */
   onBigForwardSkipEvent_: function(event) {
     this.$.audioController.bigSkip(true);
   },

   /**
    * Big skip backword.
    * @private
    */
   onBigBackwordSkipEvent_: function(event) {
     this.$.audioController.bigSkip(false);
   },
 });
	// 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.

	Polymer({
	is: 'audio-player',

	listeners: {
	'toggle-pause-event': 'onTogglePauseEvent_',
	'small-forward-skip-event': 'onSmallForwardSkipEvent_',
	'small-backword-skip-event': 'onSmallBackwordSkipEvent_',
	'big-forward-skip-event': 'onBigForwardSkipEvent_',
	'big-backword-skip-event': 'onBigBackwordSkipEvent_',
	},

	properties: {
	/**
	* Flag whether the audio is playing or paused. True if playing, or false
	* paused.
	*/
	playing: {
	type: Boolean,
	observer: 'playingChanged',
	reflectToAttribute: true
	},

	/**
	* Current elapsed time in the current music in millisecond.
	*/
	time: {
	type: Number,
	observer: 'timeChanged'
	},

	/**
	* Whether the shuffle button is ON.
	*/
	shuffle: {
	type: Boolean,
	notify: true
	},

	/**
	* Whether the repeat button is ON.
	*/
	repeat: {
	type: Boolean,
	notify: true
	},

	/**
	* The audio volume. 0 is silent, and 100 is maximum loud.
	*/
	volume: {
	type: Number,
	notify: true
	},

	/**
	* Whether the playlist is expanded or not.
	*/
	playlistExpanded: {
	type: Boolean,
	notify: true
	},
	/**
	* Whether the artwork is expanded or not.
	*/
	trackInfoExpanded: {
	type: Boolean,
	notify: true
	},

	/**
	* Track index of the current track.
	*/
	currentTrackIndex: {
	type: Number,
	observer: 'currentTrackIndexChanged'
	},

	/**
	* URL of the current track. (exposed publicly for tests)
	*/
	currenttrackurl: {
	type: String,
	value: '',
	reflectToAttribute: true
	},

	/**
	* The number of played tracks. (exposed publicly for tests)
	*/
	playcount: {
	type: Number,
	value: 0,
	reflectToAttribute: true
	},

	ariaLabels: {
	type: Object
	}
	},

	/**
	* The last playing state when user starts dragging the seek bar.
	* @private {boolean}
	*/
	wasPlayingOnDragStart_: false,

	/**
	* Initializes an element. This method is called automatically when the
	* element is ready.
	*/
	ready: function() {
	this.addEventListener('keydown', this.onKeyDown_.bind(this));

	this.$.audioController.addEventListener('dragging-changed',
	this.onDraggingChanged_.bind(this));

	this.$.audio.addEventListener('ended', this.onAudioEnded.bind(this));
	this.$.audio.addEventListener('error', this.onAudioError.bind(this));

	var onAudioStatusUpdatedBound = this.onAudioStatusUpdate_.bind(this);
	this.$.audio.addEventListener('timeupdate', onAudioStatusUpdatedBound);
	this.$.audio.addEventListener('ended', onAudioStatusUpdatedBound);
	this.$.audio.addEventListener('play', onAudioStatusUpdatedBound);
	this.$.audio.addEventListener('pause', onAudioStatusUpdatedBound);
	this.$.audio.addEventListener('suspend', onAudioStatusUpdatedBound);
	this.$.audio.addEventListener('abort', onAudioStatusUpdatedBound);
	this.$.audio.addEventListener('error', onAudioStatusUpdatedBound);
	this.$.audio.addEventListener('emptied', onAudioStatusUpdatedBound);
	this.$.audio.addEventListener('stalled', onAudioStatusUpdatedBound);
	},

	/**
	* Invoked when trackList.currentTrackIndex is changed.
	* @param {number} newValue new value.
	* @param {number} oldValue old value.
	*/
	currentTrackIndexChanged: function(newValue, oldValue) {
	var currentTrackUrl = '';

	if (oldValue != newValue) {
	var currentTrack = this.$.trackList.getCurrentTrack();
	if(currentTrack && currentTrack != this.$.trackInfo.track){
	this.$.trackInfo.track = currentTrack;
	this.$.trackInfo.artworkAvailable = !!currentTrack.artworkUrl;
	}
	if (currentTrack && currentTrack.url != this.$.audio.src) {
	this.$.audio.src = currentTrack.url;
	currentTrackUrl = this.$.audio.src;
	if (this.playing)
	this.$.audio.play();
	}
	}

	// The attributes may be being watched, so we change it at the last.
	this.currenttrackurl = currentTrackUrl;
	},

	/**
	* Invoked when playing is changed.
	* @param {boolean} newValue new value.
	* @param {boolean} oldValue old value.
	*/
	playingChanged: function(newValue, oldValue) {
	if (newValue) {
	if (!this.$.audio.src) {
	var currentTrack = this.$.trackList.getCurrentTrack();
	if (currentTrack && currentTrack.url != this.$.audio.src) {
	this.$.audio.src = currentTrack.url;
	}
	}

	if (this.$.audio.src) {
	this.currenttrackurl = this.$.audio.src;
	this.$.audio.play();
	return;
	}
	}

	// When the new status is "stopped".
	this.cancelAutoAdvance_();
	this.$.audio.pause();
	this.currenttrackurl = '';
	this.lastAudioUpdateTime_ = null;
	},

	/**
	* Invoked when time is changed.
	* @param {number} newValue new time (in ms).
	* @param {number} oldValue old time (in ms).
	*/
	timeChanged: function(newValue, oldValue) {
	// Ignores updates from the audio element.
	if (this.lastAudioUpdateTime_ === newValue)
	return;

	if (this.$.audio.readyState !== 0)
	this.$.audio.currentTime = this.time / 1000;
	},

	/**
	* Invoked when the next button in the controller is clicked.
	* This handler is registered in the 'on-click' attribute of the element.
	*/
	onControllerNextClicked: function() {
	this.advance_(true /* forward /, true / repeat */);
	},

	/**
	* Invoked when the previous button in the controller is clicked.
	* This handler is registered in the 'on-click' attribute of the element.
	*/
	onControllerPreviousClicked: function() {
	this.advance_(false /* forward /, true / repeat */);
	},

	/**
	* Invoked when the playback in the audio element is ended.
	* This handler is registered in this.ready().
	*/
	onAudioEnded: function() {
	this.playcount++;
	this.advance_(true /* forward */, this.repeat);
	},

	/**
	* Invoked when the playback in the audio element gets error.
	* This handler is registered in this.ready().
	*/
	onAudioError: function() {
	this.scheduleAutoAdvance_(true /* forward */, this.repeat);
	},

	/**
	* Invoked when the time of playback in the audio element is updated.
	* This handler is registered in this.ready().
	* @private
	*/
	onAudioStatusUpdate_: function() {
	this.time = (this.lastAudioUpdateTime_ = this.$.audio.currentTime * 1000);
	this.duration = this.$.audio.duration * 1000;
	this.playing = !this.$.audio.paused;
	},

	/**
	* Invoked when receivig a request to start playing the current music.
	*/
	onPlayCurrentTrack: function() {
	this.$.audio.play();
	},

	/**
	* Invoked when receiving a request to replay the current music from the track
	* list element.
	*/
	onReplayCurrentTrack: function() {
	// Changes the current time back to the beginning, regardless of the current
	// status (playing or paused).
	this.$.audio.currentTime = 0;
	this.time = 0;
	this.$.audio.play();
	},

	/**
	* Goes to the previous or the next track.
	* @param {boolean} forward True if next, false if previous.
	* @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.playing = isNextTrackAvailable;

	var shouldFireEvent = this.$.trackList.currentTrackIndex === nextTrackIndex;
	this.$.trackList.currentTrackIndex = nextTrackIndex;
	this.$.audio.currentTime = 0;
	// If the next track and current track is the same,
	// the event will not be fired.
	// So we will fire the event here.
	// This happenes if there is only one song.
	if (shouldFireEvent) {
	this.$.trackList.fire('current-track-index-changed');
	}
	},

	/**
	* Timeout ID of auto advance. Used internally in scheduleAutoAdvance_() and
	* cancelAutoAdvance_().
	* @type {number?}
	* @private
	*/
	autoAdvanceTimer_: null,

	/**
	* Schedules automatic advance to the next track after a timeout.
	* @param {boolean} forward True if next, false if previous.
	* @param {boolean} repeat True if repeat-mode is enabled. False otherwise.
	* @private
	*/
	scheduleAutoAdvance_: function(forward, repeat) {
	this.cancelAutoAdvance_();
	var currentTrackIndex = this.currentTrackIndex;

	var timerId = setTimeout(
	function() {
	// If the other timer is scheduled, do nothing.
	if (this.autoAdvanceTimer_ !== timerId)
	return;

	this.autoAdvanceTimer_ = null;

	// If the track has been changed since the advance was scheduled, do
	// nothing.
	if (this.currentTrackIndex !== currentTrackIndex)
	return;

	// We are advancing only if the next track is not known to be invalid.
	// This prevents an endless auto-advancing in the case when all tracks
	// are invalid (we will only visit each track once).
	this.advance_(forward, repeat);
	}.bind(this),
	3000);

	this.autoAdvanceTimer_ = timerId;
	},

	/**
	* Cancels the scheduled auto advance.
	* @private
	*/
	cancelAutoAdvance_: function() {
	if (this.autoAdvanceTimer_) {
	clearTimeout(this.autoAdvanceTimer_);
	this.autoAdvanceTimer_ = null;
	}
	},

	/**
	* The list of the tracks in the playlist.
	*
	* When it changed, current operation including playback is stopped and
	* restarts playback with new tracks if necessary.
	*
	* @type {Array<TrackInfo>}
	*/
	get tracks() {
	return this.$.trackList ? this.$.trackList.tracks : null;
	},
	set tracks(tracks) {
	if (this.$.trackList.tracks === tracks)
	return;

	this.cancelAutoAdvance_();

	this.$.trackList.tracks = tracks;
	var currentTrack = this.$.trackList.getCurrentTrack();
	if (currentTrack && currentTrack.url != this.$.audio.src) {
	this.$.audio.src = currentTrack.url;
	this.$.audio.play();
	}
	},

	/**
	* Notifis the track-list element that the metadata for specified track is
	* updated.
	* @param {number} index The index of the track whose metadata is updated.
	*/
	notifyTrackMetadataUpdated: function(index) {
	if (index < 0 \|\| index >= this.tracks.length)
	return;

	this.$.trackList.notifyPath('tracks.' + index + '.title',
	this.tracks[index].title);
	this.$.trackList.notifyPath('tracks.' + index + '.artist',
	this.tracks[index].artist);

	if (this.$.trackInfo.track &&
	this.$.trackInfo.track.url === this.tracks[index].url){
	this.$.trackInfo.notifyPath('track.title', this.tracks[index].title);
	this.$.trackInfo.notifyPath('track.artist', this.tracks[index].artist);
	var artworkUrl = this.tracks[index].artworkUrl;
	if (artworkUrl) {
	this.$.trackInfo.notifyPath('track.artworkUrl',
	this.tracks[index].artworkUrl);
	this.$.trackInfo.artworkAvailable = true;
	} else {
	this.$.trackInfo.notifyPath('track.artworkUrl', undefined);
	this.$.trackInfo.artworkAvailable = false;
	}
	}
	},

	/**
	* Invoked when the audio player is being unloaded.
	*/
	onPageUnload: function() {
	this.$.audio.src = ''; // Hack to prevent crashing.
	},

	/**
	* Invoked when dragging state of seek bar on control panel is changed.
	* During the user is dragging it, audio playback is paused temporalily.
	*/
	onDraggingChanged_: function() {
	if (this.$.audioController.dragging) {
	if (this.playing) {
	this.wasPlayingOnDragStart_ = true;
	this.$.audio.pause();
	}
	} else {
	if (this.wasPlayingOnDragStart_) {
	this.$.audio.play();
	this.wasPlayingOnDragStart_ = false;
	}
	}
	},

	/**
	* Invoked when the 'keydown' event is fired.
	* @param {Event} event The event object.
	*/
	onKeyDown_: function(event) {
	switch (event.key) {
	case 'MediaTrackNext':
	this.onControllerNextClicked();
	break;
	case 'MediaPlayPause':
	this.playing = !this.playing;
	break;
	case 'MediaTrackPrevious':
	this.onControllerPreviousClicked();
	break;
	case 'MediaStop':
	// TODO: Define "Stop" behavior.
	break;
	}
	},

	/**
	* Computes volume value for audio element. (should be in [0.0, 1.0])
	* @param {number} volume Volume which is set in the UI. ([0, 100])
	* @return {number}
	*/
	computeAudioVolume_: function(volume) {
	return volume / 100;
	},

	/**
	* Toggle pause.
	* @private
	*/
	onTogglePauseEvent_: function(event) {
	this.$.audioController.playClick();
	},

	/**
	* Small skip forward.
	* @private
	*/
	onSmallForwardSkipEvent_: function(event) {
	this.$.audioController.smallSkip(true);
	},

	/**
	* Small skip backword.
	* @private
	*/
	onSmallBackwordSkipEvent_: function(event) {
	this.$.audioController.smallSkip(false);
	},

	/**
	* Big skip forward.
	* @private
	*/
	onBigForwardSkipEvent_: function(event) {
	this.$.audioController.bigSkip(true);
	},

	/**
	* Big skip backword.
	* @private
	*/
	onBigBackwordSkipEvent_: function(event) {
	this.$.audioController.bigSkip(false);
	},
	});