Fix some accessibility issues in image editing.

ui/file_manager/gallery/js/image_editor/image_transform.js

Index: ui/file_manager/gallery/js/image_editor/image_transform.js
diff --git a/ui/file_manager/gallery/js/image_editor/image_transform.js b/ui/file_manager/gallery/js/image_editor/image_transform.js
index 2f06b831d595668c6ebd09db40ff3bae992474cd..aa5ae345a9dc043e9c78c77233794768068206b0 100644
--- a/ui/file_manager/gallery/js/image_editor/image_transform.js
+++ b/ui/file_manager/gallery/js/image_editor/image_transform.js
@@ -143,6 +143,7 @@ ImageEditor.Mode.Crop.prototype.createTools = function(toolbar) {
     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,