Get rid of AX_LINE_BREAKS attribute to improve performance.

chrome/test/data/extensions/api_test/automation/tests/tabs/line_start_offsets.js

Index: chrome/test/data/extensions/api_test/automation/tests/tabs/line_start_offsets.js
diff --git a/chrome/test/data/extensions/api_test/automation/tests/tabs/line_start_offsets.js b/chrome/test/data/extensions/api_test/automation/tests/tabs/line_start_offsets.js
new file mode 100644
index 0000000000000000000000000000000000000000..bd20ed72c2070febd3b38181a97676f342d34c63
--- /dev/null
+++ b/chrome/test/data/extensions/api_test/automation/tests/tabs/line_start_offsets.js
@@ -0,0 +1,27 @@
+// Copyright 2016 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.
+
+var allTests = [
+  function testInput() {
+    var input = rootNode.find({ id: 'input' });
+    assertTrue('lineStartOffsets' in input);
+    var line_starts = input.lineStartOffsets;
+    assertEq(1, line_starts.length());
+    assertEq(0, line_starts[i]);
+    chrome.test.succeed();
+  },
+
+  function testTextarea() {
+    var textarea = rootNode.find({ id: 'textarea' });
+    assertTrue('lineStartOffsets' in textarea);
+    var line_starts = textarea.lineStartOffsets;
+    assertEq(3, line_starts.length());
+    assertEq(0, line_starts[0]);
+    assertEq(7, line_starts[1]);
+    assertEq(15, line_starts[2]);
+    chrome.test.succeed();
+  }
+];
+
+setUpAndRunTests(allTests, 'line_start_offsets.html');