[SyncFS] Make MetadataDatabase operations synchronous

chrome/browser/sync_file_system/drive_backend/uninstall_app_task.cc

 // 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.
 
 #include "chrome/browser/sync_file_system/drive_backend/uninstall_app_task.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "chrome/browser/drive/drive_api_util.h"
 #include "chrome/browser/drive/drive_service_interface.h"
@@ skipping 23 matching lines @@
 UninstallAppTask::~UninstallAppTask() {
 }
 
 void UninstallAppTask::RunExclusive(const SyncStatusCallback& callback) {
   if (!IsContextReady()) {
     callback.Run(SYNC_STATUS_FAILED);
     return;
   }
 
   if (uninstall_flag_ == RemoteFileSyncService::UNINSTALL_AND_KEEP_REMOTE) {
-    metadata_database()->UnregisterApp(app_id_, callback);
+    SyncStatusCode status = metadata_database()->UnregisterApp(app_id_);
+    callback.Run(status);
     return;
   }
   DCHECK_EQ(RemoteFileSyncService::UNINSTALL_AND_PURGE_REMOTE, uninstall_flag_);
 
   int64 sync_root_tracker_id = metadata_database()->GetSyncRootTrackerID();
   TrackerIDSet trackers;
   if (!metadata_database()->FindTrackersByParentAndTitle(
           sync_root_tracker_id, app_id_, &trackers) ||
       !trackers.has_active()) {
     callback.Run(SYNC_STATUS_OK);
@@ skipping 22 matching lines @@
 void UninstallAppTask::DidDeleteAppRoot(const SyncStatusCallback& callback,
                                         int64 change_id,
                                         google_apis::GDataErrorCode error) {
   SyncStatusCode status = GDataErrorCodeToSyncStatusCode(error);
   if (status != SYNC_STATUS_OK &&
       error != google_apis::HTTP_NOT_FOUND) {
     callback.Run(SYNC_STATUS_FAILED);
     return;
   }
 
-  metadata_database()->UnregisterApp(app_id_, callback);
+  status = metadata_database()->UnregisterApp(app_id_);
+  callback.Run(status);
 }
 
 bool UninstallAppTask::IsContextReady() {
   return sync_context_->GetMetadataDatabase() &&
       sync_context_->GetDriveService();
 }
 
 MetadataDatabase* UninstallAppTask::metadata_database() {
   return sync_context_->GetMetadataDatabase();
 }
 
 drive::DriveServiceInterface* UninstallAppTask::drive_service() {
   set_used_network(true);
   return sync_context_->GetDriveService();
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system