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

chrome/browser/extensions/extension_browsertest.h

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_EXTENSION_BROWSERTEST_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_BROWSERTEST_H_
 
 #include <string>
 
 #include "base/command_line.h"
@@ skipping 307 matching lines @@
 
 #if defined(OS_CHROMEOS)
   // True if the command line should be tweaked as if ChromeOS user is
   // already logged in.
   bool set_chromeos_user_;
 #endif
 
   // test_data/extensions.
   base::FilePath test_data_dir_;
 
-  std::unique_ptr<ChromeExtensionTestNotificationObserver> observer_;
+  std::unique_ptr<extensions::ChromeExtensionTestNotificationObserver>
+      observer_;
 
  private:
   // Temporary directory for testing.
   base::ScopedTempDir temp_dir_;
 
   // Specifies the type of UI (if any) to show during installation and what
   // user action to simulate.
   enum InstallUIType {
     INSTALL_UI_TYPE_NONE,
     INSTALL_UI_TYPE_CANCEL,
@@ skipping 47 matching lines @@
 #endif
 
   // The default profile to be used.
   Profile* profile_;
 
   // Cache cache implementation.
   std::unique_ptr<extensions::ExtensionCacheFake> test_extension_cache_;
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_BROWSERTEST_H_