Improve braille related message descriptions and clean up message handling in Chromevox.

chrome/browser/resources/chromeos/chromevox/walkers/group_walker.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.
 
 /**
  * @fileoverview A class for walking "groups". Groups, intuitively, are logical
  * collections of dom elements. See AbstractNodeWalker and the
  * stopNodeDescent() method here for how groups are defined.
  */
 
@@ skipping 30 matching lines @@
  * @override
  */
 cvox.GroupWalker.prototype.getBraille = function(prevSel, sel) {
   throw 'getBraille is unsupported';
 };
 
 /**
  * @override
  */
 cvox.GroupWalker.prototype.getGranularityMsg = function() {
-  return cvox.ChromeVox.msgs.getMsg('group_strategy');
+  return Msgs.getMsg('group_strategy');
 };
 
 /**
  * @override
  */
 cvox.GroupWalker.prototype.stopNodeDescent = function(node) {
   return cvox.GroupUtil.isLeafNode(node);
 };