chrome: Cleanup class/struct forward declarations

chrome/browser/extensions/extension_prefs_unittest.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_PREFS_UNITTEST_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_PREFS_UNITTEST_H_
 
 #include <stddef.h>
 
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
 #include "chrome/browser/extensions/test_extension_prefs.h"
 #include "content/public/test/test_browser_thread.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
-namespace base {
-class Value;
-}
-
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
 
 namespace extensions {
 class ChromeAppSorting;
 class Extension;
 
 // Base class for extension preference-related unit tests.
 class ExtensionPrefsTest : public testing::Test {
@@ skipping 51 matching lines @@
   scoped_refptr<Extension> extension3_;
   scoped_refptr<Extension> extension4_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PrefsPrepopulatedTestBase);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_PREFS_UNITTEST_H_