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

chrome/browser/resources/chromeos/chromevox/walkers/structural_line_walker_test.unitjs

 // 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.
 
 // Include test fixture.
 GEN_INCLUDE(['../testing/chromevox_unittest_base.js']);
 
 /**
  * Test fixture.
  * @constructor
  * @extends {ChromeVoxUnitTestBase}
  */
 function CvoxStructuralLineWalkerUnitTest() {}
 
 CvoxStructuralLineWalkerUnitTest.prototype = {
   __proto__: ChromeVoxUnitTestBase.prototype,
 
   /** @override */
   closureModuleDeps: [
     'cvox.StructuralLineWalker',
-    'cvox.TestMsgs',
+    'TestMsgs',
   ],
 
   /** @override */
   setUp: function() {
     this.loadDoc(function() {/*!
       <a id='1' href='google.com'>Click Here</a>
       <pre id='2'>This text will break
         immediately here!
         <a href='google.com'>And here!</a>
       </p>
       */});
   
-    cvox.ChromeVox.msgs = new cvox.TestMsgs();
+    Msgs = TestMsgs;
   
     this.walker_ = new cvox.StructuralLineWalker();
   },
 };
 
 TEST_F('CvoxStructuralLineWalkerUnitTest', 'BrailleLine', function() {
   var aLink = $('1');
   var aLinkSel1 = this.walker_.sync(cvox.CursorSelection.fromNode(aLink));
   assertEquals('Click Here lnk',
                this.walker_.getBraille(aLinkSel1, aLinkSel1).text.toString());
@@ skipping 69 matching lines @@
   assertEquals('1. orange',
                this.walker_.getBraille(li1Sel, li1Sel).text.toString());
   assertEquals('2. apple',
                this.walker_.getBraille(li2Sel, li2Sel).text.toString());
   assertEquals(
           '3. hi broken',
       this.walker_.getBraille(li3Sel, li3Sel).text.toString());
   assertEquals('line here',
                this.walker_.getBraille(li3SelNext, li3SelNext).text.toString());
 });