Fix some accessibility issues in image editing.

ui/file_manager/gallery/js/image_editor/image_transform.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.
 
 /**
  * Crop mode.
  *
  * @extends {ImageEditor.Mode}
  * @constructor
  * @struct
@@ skipping 125 matching lines @@
  * @override
  */
 ImageEditor.Mode.Crop.prototype.createTools = function(toolbar) {
   var aspects = {
     GALLERY_ASPECT_RATIO_1_1: 1 / 1,
     GALLERY_ASPECT_RATIO_6_4: 6 / 4,
     GALLERY_ASPECT_RATIO_7_5: 7 / 5,
     GALLERY_ASPECT_RATIO_16_9: 16 / 9
   };
 
+  // TODO(fukino): The loop order is not guaranteed. Fix it!

[oka, 2016/10/06 09:11:55]

suggestion: Consider using Map.
A Map object iterates its elements in insertion order.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Obje...

You can revert this TODO if it's not relevant to the objective of this CL (up to
you).

[fukino, 2016/10/06 14:34:30]

Map can be used if tooling support works well. I'll check it later. (I heard it
used to have problems before.)
Let me keep this comment to skip one additional CL. Sorry!

   for (var name in aspects) {
     var button = toolbar.addButton(
         name,
         ImageEditor.Toolbar.ButtonType.LABEL,
         this.onCropAspectRatioClicked_.bind(this, toolbar, aspects[name]),
         'crop-aspect-ratio');
 
     // Prevent from cropping by Enter key if the button is focused.
     button.addEventListener('keydown', function(event) {
       var key = util.getKeyModifiers(event) + event.key;
@@ skipping 581 matching lines @@
       break;
     case 'bottom':
       this.bounds_.bottom = this.bounds_.top + newHeight;
       break;
     case 'none':
       this.bounds_.top = middle - newHeight / 2;
       this.bounds_.bottom = middle + newHeight / 2;
       break;
   }
 };