Remove file-level 'use strict' from file_manager.

ui/file_manager/gallery/js/error_banner.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';
-
 /**
  * @param {Element} container Content container.
  * @constructor
  */
 function ErrorBanner(container) {
   this.container_ = container;
   this.errorBanner_ = this.container_.querySelector('.error-banner');
 }
 
 /**
  * Shows an error message.
  * @param {string} message Message.
  */
 ErrorBanner.prototype.show = function(message) {
   this.errorBanner_.textContent = str(message);
   this.container_.setAttribute('error', true);
 };
 
 /**
  * Hides an error message.
  */
 ErrorBanner.prototype.clear = function() {
   this.container_.removeAttribute('error');
 };