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

chrome/browser/chromeos/policy/device_cloud_policy_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 <memory>
 
 #include "base/command_line.h"
 #include "base/files/dir_reader_posix.h"
 #include "base/files/file_path.h"
 #include "base/memory/ptr_util.h"
@@ skipping 193 matching lines @@
  protected:
   SigninExtensionsDeviceCloudPolicyBrowserTest()
       : fetcher_factory_(&fetcher_impl_factory_) {}
 
   const extensions::Extension* InstallAndLoadTestExtension() const {
     Profile* signin_profile = GetSigninProfile();
     ExtensionService* service =
         extensions::ExtensionSystem::Get(signin_profile)->extension_service();
     scoped_refptr<extensions::UnpackedInstaller> installer(
         extensions::UnpackedInstaller::Create(service));
-    ExtensionTestNotificationObserver observer(signin_profile);
+    extensions::ExtensionTestNotificationObserver observer(signin_profile);
     installer->Load(GetTestExtensionSourcePath());
     observer.WaitForExtensionLoad();
     return GetTestExtension();
   }
 
  private:
   void SetUp() override {
     StartPolicyTestServer();
     DevicePolicyCrosBrowserTest::SetUp();
   }
@@ skipping 139 matching lines @@
   ASSERT_TRUE(extension);
   Browser* browser = CreateBrowser(GetSigninProfile());
   extensions::ResultCatcher result_catcher;
   ui_test_utils::NavigateToURL(
       browser, extension->GetResourceURL(kTestExtensionTestPage));
   EXPECT_TRUE(result_catcher.GetNextResult());
   CloseBrowserSynchronously(browser);
 }
 
 }  // namespace policy