Get rid of AX_LINE_BREAKS attribute to improve performance.

chrome/browser/resources/chromeos/chromevox/common/chrome_extension_externs.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 Definitions for the Chromium extensions API used by ChromeVox.
  *
  * @externs
  */
@@ skipping 594 matching lines @@
 chrome.automation.anchorOffset;
 
 /**
  * @type {(chrome.automation.AutomationNode|undefined)}
  */
 chrome.automation.AutomationNode.prototype.focusObject;
 
 /**
  * @type {(Array<number>|undefined)}
  */
-chrome.automation.AutomationNode.prototype.lineBreaks;
+chrome.automation.AutomationNode.prototype.lineStartOffsets;
 
 /**
  * @type {(number|undefined)}
  */
 chrome.automation.focusOffset;
 
 /**
  * @type {(chrome.automation.AutomationNode|undefined)}
  */
 chrome.automation.AutomationNode.prototype.activeDescendant;
@@ skipping 44 matching lines @@
  */
 chrome.automation.AutomationRootNode.prototype.focusObject;
 
 /**
  * @type {number}
  */
 chrome.automation.AutomationRootNode.prototype.focusOffset;
 
 /** @type {function() : !Object} */
 chrome.app.getDetails;