cvox2: Fix a typo causing the wrong variable to be referenced.

chrome/browser/resources/chromeos/chromevox/cvox2/background/background.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 The entry point for all ChromeVox2 related code for the
  * background page.
  */
 
 goog.provide('Background');
@@ skipping 461 matching lines @@
 
     new Output().withSpeechAndBraille(range, null, evt.type).go();
   },
 
   /**
    * Provides all feedback once a focus event fires.
    * @param {Object} evt
    */
   onFocus: function(evt) {
     // Invalidate any previous editable text handler state.
-    this.editableTextHandler = null;
+    this.editableTextHandler_ = null;
 
     var node = evt.target;
 
     // It almost never makes sense to place focus directly on a rootWebArea.
     if (node.role == RoleType.rootWebArea) {
       // Try to find a focusable descendant.
       node = AutomationUtil.findNodePost(node,
                                          Dir.FORWARD,
                                          AutomationPredicate.focused) || node;
 
@@ skipping 297 matching lines @@
               node.state.protected,
               cvox.ChromeVox.tts);
     }
   }
 };
 
 /** @type {Background} */
 global.backgroundObj = new Background();
 
 });  // goog.scope