Remove file-level 'use strict' from file_manager.

ui/file_manager/gallery/js/mosaic_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';
-
 /**
  * @param {Element} container Content container.
  * @param {ErrorBanner} errorBanner Error banner.
  * @param {cr.ui.ArrayDataModel} dataModel Data model.
  * @param {cr.ui.ListSelectionModel} selectionModel Selection model.
  * @param {VolumeManagerWrapper} volumeManager Volume manager.
  * @param {function()} toggleMode Function to switch to the Slide mode.
  * @constructor
  */
 function MosaicMode(
@@ skipping 1987 matching lines @@
   return new ImageRect(this.left_ - this.container_.scrollLeft, this.top_,
       this.width_, this.height_).inflate(-margin, -margin);
 };
 
 /**
  * @return {number} X coordinate of the tile center.
  */
 Mosaic.Tile.prototype.getCenterX = function() {
   return this.left_ + Math.round(this.width_ / 2);
 };