chrome: Cleanup class/struct forward declarations

chrome/browser/sync_file_system/drive_backend/drive_backend_test_util.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 CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_DRIVE_BACKEND_TEST_UTIL_H_
 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_DRIVE_BACKEND_TEST_UTIL_H_
 
 #include <stdint.h>
 
 #include <memory>
 
 #include "chrome/browser/sync_file_system/sync_status_code.h"
 #include "google_apis/drive/drive_api_error_codes.h"
 
 namespace google_apis {
 class FileResource;
 }
 
 namespace sync_file_system {
 namespace drive_backend {
 
 class FileDetails;
 class FileMetadata;
 class FileTracker;
-class MetadataDatabase;
-class ServiceMetadata;
 
 namespace test_util {
 
 void ExpectEquivalentDetails(const FileDetails& left, const FileDetails& right);
 void ExpectEquivalentMetadata(const FileMetadata& left,
                               const FileMetadata& right);
 void ExpectEquivalentTrackers(const FileTracker& left,
                               const FileTracker& right);
 
 std::unique_ptr<FileMetadata> CreateFolderMetadata(const std::string& file_id,
@@ skipping 16 matching lines @@
 };
 
 // Returns the kind of the given FileResourceKind.
 FileResourceKind GetFileResourceKind(const google_apis::FileResource& resource);
 
 }  // namespace test_util
 }  // namespace drive_backend
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_DRIVE_BACKEND_TEST_UTIL_H_