chrome: Cleanup class/struct forward declarations

chrome/browser/extensions/api/permissions/permissions_api_helpers.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_API_PERMISSIONS_PERMISSIONS_API_HELPERS_H_
 #define CHROME_BROWSER_EXTENSIONS_API_PERMISSIONS_PERMISSIONS_API_HELPERS_H_
 
 #include <memory>
 #include <string>
 
 #include "base/memory/ref_counted.h"
 
-namespace base {
-class DictionaryValue;
-}
-
 namespace extensions {
 
 class PermissionSet;
 
 namespace api {
 namespace permissions {
 struct Permissions;
 }
 }
 
 namespace permissions_api_helpers {
 
 // Converts the permission |set| to a permissions object.
 std::unique_ptr<api::permissions::Permissions> PackPermissionSet(
     const PermissionSet& set);
 
 // Creates a permission set from |permissions|. Returns NULL if the permissions
 // cannot be converted to a permission set, in which case |error| will be set.
 std::unique_ptr<const PermissionSet> UnpackPermissionSet(
     const api::permissions::Permissions& permissions,
     bool allow_file_access,
     std::string* error);
 
 }  // namespace permissions_api_helpers
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_PERMISSIONS_PERMISSIONS_API_HELPERS_H_