FBTF: Forward declare and move constructors in chrome/common/extensions/.

chrome/browser/extensions/external_pref_extension_provider.h

 // Copyright (c) 2009 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_EXTERNAL_PREF_EXTENSION_PROVIDER_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTERNAL_PREF_EXTENSION_PROVIDER_H_
 #pragma once
 
 #include <set>
 #include <string>
 
 #include "chrome/browser/extensions/external_extension_provider.h"
 
 class DictionaryValue;
+class ValueSerializer;
 class Version;
 
 // A specialization of the ExternalExtensionProvider that uses a json file to
 // look up which external extensions are registered.
 class ExternalPrefExtensionProvider : public ExternalExtensionProvider {
  public:
   explicit ExternalPrefExtensionProvider();
   virtual ~ExternalPrefExtensionProvider();
 
   // Used only during testing to not use the json file for external extensions,
   // but instead parse a json file specified by the test.
   void SetPreferencesForTesting(const std::string& json_data_for_testing);
 
   // ExternalExtensionProvider implementation:
   virtual void VisitRegisteredExtension(
       Visitor* visitor, const std::set<std::string>& ids_to_ignore) const;
 
   virtual Version* RegisteredVersion(const std::string& id,
                                      Extension::Location* location) const;
  protected:
   scoped_ptr<DictionaryValue> prefs_;
 
  private:
   void SetPreferences(ValueSerializer* serializer);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTERNAL_PREF_EXTENSION_PROVIDER_H_