Remove file-level 'use strict' from file_manager.

ui/file_manager/audio_player/js/background.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';
-
 /**
  * Icon of the audio player.
  * TODO(yoshiki): Consider providing an exact size icon, instead of relying
  * on downsampling by ash.
  *
  * @type {string}
  * @const
  */
 var AUDIO_PLAYER_ICON = 'audio_player/icons/audio-player-64.png';
 
@@ skipping 140 matching lines @@
       audioPlayer.launch({items: urls, position: position}, reopen, fulfill);
     });
   }).then(function() {
     audioPlayer.setIcon('icons/audio-player-64.png');
     AppWindowWrapper.focusOnDesktop(audioPlayer.rawAppWindow);
   }).catch(function(error) {
     console.error('Launch failed' + error.stack || error);
     return Promise.reject(error);
   });
 }