extensions: Cleanup class/struct fwd declarations

extensions/shell/test/shell_test.h

 // 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.
 
 #ifndef EXTENSIONS_SHELL_TEST_SHELL_TEST_H_
 #define EXTENSIONS_SHELL_TEST_SHELL_TEST_H_
 
 #include <memory>
 
 #include "content/public/test/browser_test.h"
 #include "content/public/test/browser_test_base.h"
 #include "extensions/common/features/feature_channel.h"
 
-namespace base {
-class FilePath;
-}
-
 namespace content {
 class BrowserContext;
 }
 
 namespace extensions {
 
 class ShellExtensionSystem;
 
 // Base class for app shell browser tests.
 class AppShellTest : public content::BrowserTestBase {
@@ skipping 10 matching lines @@
 
  protected:
   content::BrowserContext* browser_context_;
   ShellExtensionSystem* extension_system_;
   ScopedCurrentChannel current_channel_;
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_SHELL_TEST_SHELL_TEST_H_