Remove file-level 'use strict' from file_manager.

ui/file_manager/video_player/js/cast/media_manager.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';
-
 /**
  * Media manager class.
  * This class supports the information for the media file.
  * @param {FileEntry} entry Entry of media file. This must be a external entry.
  * @constructor
  */
 function MediaManager(entry) {
   this.entry_ = entry;
 
   this.cachedDriveProp_ = null;
@@ skipping 118 matching lines @@
         [this.entry_.toURL()], fulfill);
   }.bind(this)).then(function(props) {
     if (!props || !props[0]) {
       return Promise.reject('Thumbnail fetch failed.');
     } else {
       this.cachedDriveProp_ = props[0];
       return props[0].thumbnailUrl || '';
     }
   }.bind(this));
 };