Remove file-level 'use strict' from file_manager.

ui/file_manager/gallery/js/slide_mode.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';
-
 /**
  * Slide mode displays a single image and has a set of controls to navigate
  * between the images and to edit an image.
  *
  * @param {Element} container Main container element.
  * @param {Element} content Content container element.
  * @param {Element} toolbar Toolbar element.
  * @param {ImageEditor.Prompt} prompt Prompt.
  * @param {ErrorBanner} errorBanner Error banner.
  * @param {cr.ui.ArrayDataModel} dataModel Data model.
@@ skipping 1545 matching lines @@
 TouchHandler.prototype.onMouseWheel_ = function(event) {
   var viewport = this.slideMode_.getViewport();
   if (!this.enabled_ || !viewport.isZoomed())
     return;
   this.stopOperation();
   viewport.setOffset(
       viewport.getOffsetX() + event.wheelDeltaX,
       viewport.getOffsetY() + event.wheelDeltaY);
   this.slideMode_.applyViewportChange();
 };