Get rid of AX_LINE_BREAKS attribute to improve performance.

chrome/browser/resources/chromeos/chromevox/cvox2/background/editing.js

 // Copyright 2015 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 Processes events related to editing text and emits the
  * appropriate spoken and braille feedback.
  */
 
 goog.provide('editing.TextEditHandler');
@@ skipping 115 matching lines @@
         this.node_.textSelEnd,
         true /* triggered by user */);
     this.changed(textChangeEvent);
     this.outputBraille_();
   },
 
   /** @override */
   getLineIndex: function(charIndex) {
     if (!this.multiline)
       return 0;
-    var breaks = this.node_.lineBreaks || [];
+    var breaks = this.node_.lineStartOffsets || [];
     var index = 0;
     while (index < breaks.length && breaks[index] <= charIndex)
       ++index;
     return index;
   },
 
   /** @override */
   getLineStart: function(lineIndex) {
     if (!this.multiline || lineIndex == 0)
       return 0;
@@ skipping 12 matching lines @@
     if (0 < end && value[end - 1] == '\n')
       return end - 1;
     return end;
   },
 
   /**
    * @return {Array<number>}
    * @private
    */
   getLineBreaks_: function() {
-    // node.lineBreaks is undefined when the multiline field has no line
+    // node.lineStartOffsets is undefined when the multiline field has no line
     // breaks.
-    return this.node_.lineBreaks || [];
+    return this.node_.lineStartOffsets || [];
   },
 
   /** @private */
   outputBraille_: function() {
     var isFirstLine = false;  // First line in a multiline field.
     var output = new Output();
     var range;
     if (this.multiline) {
       var lineIndex = this.getLineIndex(this.start);
       if (lineIndex == 0) {
@@ skipping 28 matching lines @@
     testNode = testNode.parent;
   } while (testNode);
 
   if (rootFocusedEditable)
     return new TextFieldTextEditHandler(rootFocusedEditable);
 
   return null;
 };
 
 });