Make |context| passed to queryRequiredElement optional

ui/file_manager/gallery/js/image_editor/image_editor.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.
 
 /**
  * ImageEditor is the top level object that holds together and connects
  * everything needed for image editing.
  *
  * @param {!Viewport} viewport The viewport.
  * @param {!ImageView} imageView The ImageView containing the images to edit.
@@ skipping 91 matching lines @@
    */
   this.redoButton_ = this.createToolButton_('redo', 'GALLERY_REDO',
       this.redo.bind(this));
   this.registerAction_('redo');
 
   /**
    * @private {!HTMLElement}
    * @const
    */
   this.exitButton_ = /** @type {!HTMLElement} */
-      (queryRequiredElement(document, '.edit-mode-toolbar paper-button.exit'));
+      (queryRequiredElement('.edit-mode-toolbar paper-button.exit'));
   this.exitButton_.addEventListener('click', this.onExitClicked_.bind(this));
 
   /**
    * @private {!FilesToast}
    */
   this.filesToast_ = /** @type {!FilesToast}*/
-      (queryRequiredElement(document, 'files-toast'));
+      (queryRequiredElement('files-toast'));
 }
 
 ImageEditor.prototype.__proto__ = cr.EventTarget.prototype;
 
 /**
  * Handles click event of exit button.
  * @private
  */
 ImageEditor.prototype.onExitClicked_ = function() {
   var event = new Event('exit-clicked');
@@ skipping 1301 matching lines @@
 
 /**
  * Hide the prompt.
  */
 ImageEditor.Prompt.prototype.hide = function() {
   if (!this.prompt_) return;
   this.prompt_.setAttribute('state', 'fadeout');
   // Allow some time for the animation to play out.
   this.setTimer(this.reset.bind(this), 500);
 };