Removing chrome.pushMessaging API

chrome/test/data/extensions/api_test/push_messaging/get_channel_id.js

-// Copyright (c) 2012 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.
-
-function channelIdCallback(message) {
-  chrome.test.assertEq(message.channelId, "");
-}
-
-function testGetChannelId() {
-  // the api call should fail because no user is signed in
-  chrome.pushMessaging.getChannelId(
-      false, chrome.test.callbackFail("The user is not signed in.",
-                                      channelIdCallback));
-}
-
-chrome.test.runTests([testGetChannelId]);