[GCM] Make GCM API not work in incognito mode

chrome/test/data/extensions/api_test/gcm/functions/incognito/test.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.
+
+chrome.test.runTests([
+  function testIncognito() {
+    chrome.gcm.register(["Sender"], function(registrationId) {
+      chrome.test.assertEq(chrome.runtime.lastError != undefined,
+                           chrome.extension.inIncognitoContext);
+      chrome.test.succeed();
+    });
+  }
+]);