[Extensions] Move [Chrome]ExtensionTestNotificationObserver into extensions::

chrome/browser/chromeos/login/signin/oauth2_browsertest.cc

 // 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.
 
 #include <string>
 #include <utility>
 
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/stringprintf.h"
@@ skipping 748 matching lines @@
 }
 
 IN_PROC_BROWSER_TEST_F(MergeSessionTest, XHRThrottle) {
   StartNewUserSession(false);
 
   // Wait until we get send merge session request.
   WaitForMergeSessionToStart();
 
   // Reset ExtensionBrowserTest::observer_ to the right browser object.
   Browser* browser = FindOrCreateVisibleBrowser(profile());
-  observer_.reset(new ChromeExtensionTestNotificationObserver(browser));
+  observer_.reset(
+      new extensions::ChromeExtensionTestNotificationObserver(browser));
 
   // Run background page tests. The tests will just wait for XHR request
   // to complete.
   extensions::ResultCatcher catcher;
 
   std::unique_ptr<ExtensionTestMessageListener> non_google_xhr_listener(
       new ExtensionTestMessageListener("non-google-xhr-received", false));
 
   // Load extension with a background page. The background page will
   // attempt to load |fake_google_page_url_| via XHR.
@@ skipping 26 matching lines @@
 
   if (!catcher.GetNextResult()) {
     std::string message = catcher.message();
     ADD_FAILURE() << "Tests failed: " << message;
   }
 
   EXPECT_TRUE(fake_google_.IsPageRequested());
 }
 
 }  // namespace chromeos