extensions: Cleanup class/struct fwd declarations

extensions/common/extensions_client.h

 // Copyright 2013 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_COMMON_EXTENSIONS_CLIENT_H_
 #define EXTENSIONS_COMMON_EXTENSIONS_CLIENT_H_
 
 #include <memory>
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/strings/string_piece.h"
 #include "extensions/common/permissions/api_permission_set.h"
 
 class GURL;
 
 namespace base {
 class FilePath;
 }
 
 namespace extensions {
 
 class APIPermissionSet;
 class Extension;
-class ExtensionAPI;
 class FeatureProvider;
 class JSONFeatureProviderSource;
-class ManifestPermissionSet;
-class PermissionMessage;
 class PermissionMessageProvider;
-class SimpleFeature;
 class URLPatternSet;
 
 // Sets up global state for the extensions system. Should be Set() once in each
 // process. This should be implemented by the client of the extensions system.
 class ExtensionsClient {
  public:
   typedef std::vector<std::string> ScriptingWhitelist;
 
   virtual ~ExtensionsClient() {}
 
@@ skipping 92 matching lines @@
   // Return the extensions client.
   static ExtensionsClient* Get();
 
   // Initialize the extensions system with this extensions client.
   static void Set(ExtensionsClient* client);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_COMMON_EXTENSIONS_CLIENT_H_