[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 testRegister() {
-    var senderIds = ["Sender1", "Sender2"];
-    chrome.gcm.register(senderIds, function(registrationId) {
+  function testIncognito() {
+    chrome.gcm.register(["Sender"], function(registrationId) {
+      chrome.test.assertEq(chrome.runtime.lastError != undefined,
+                           chrome.extension.inIncognitoContext);
       chrome.test.succeed();
     });
   }
 ]);