Fix accessibility issues in AudioPlayer and VideoPlayer.

ui/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.
 
 Polymer({
   is: 'audio-player',
 
   properties: {
     /**
      * Flag whether the audio is playing or paused. True if playing, or false
@@ skipping 80 matching lines @@
       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,
 
   /**
@@ skipping 374 matching lines @@
 
   /**
    * 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;
   }
 });