Implement AutomationNode.querySelector().

chrome/test/data/extensions/api_test/automation/tests/tabs/query.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.
+
+var allTests = [
+  function testQuery() {
+    var cancelButton = rootNode.firstChild().lastChild();
+    function assertCorrectResult(queryResult) {
+      console.log("cancelButton: " + cancelButton.toString());

[Devlin, 2014/10/29 21:23:43]

These logs should be removed before committing (just making a note, no need to
remove them now).

[aboxhall, 2014/10/30 18:34:18]

Acknowledged.

+      console.log("queryResult: " + queryResult.toString());
+      assertEq(queryResult, cancelButton);
+      chrome.test.succeed();
+    }
+    rootNode.query({'selector': 'body > button:nth-of-type(2)'},
+                   assertCorrectResult);
+  }
+];
+
+setUpAndRunTests(allTests);