chrome: Cleanup class/struct forward declarations

chrome/browser/sync_file_system/drive_backend/fake_sync_worker.h

Index: chrome/browser/sync_file_system/drive_backend/fake_sync_worker.h
diff --git a/chrome/browser/sync_file_system/drive_backend/fake_sync_worker.h b/chrome/browser/sync_file_system/drive_backend/fake_sync_worker.h
index 12295fd5c4e0e01a0a823b682082c30810af7109..03dc73938965fbbcf89ce5f9dae227089b71af8b 100644
--- a/chrome/browser/sync_file_system/drive_backend/fake_sync_worker.h
+++ b/chrome/browser/sync_file_system/drive_backend/fake_sync_worker.h
@@ -25,11 +25,6 @@ class FilePath;
 class ListValue;
 }
 
-namespace drive {
-class DriveServiceInterface;
-class DriveUploaderInterface;
-}
-
 namespace storage {
 class FileSystemURL;
 }
@@ -41,10 +36,8 @@ class SyncFileMetadata;
 
 namespace drive_backend {
 
-class MetadataDatabase;
 class RemoteChangeProcessorOnWorker;
 class SyncEngineContext;
-class SyncTaskManager;
 
 class FakeSyncWorker : public SyncWorkerInterface {
  public: