Revert of [SyncFS] Post tasks between SyncEngine and SyncWorker

chrome/browser/sync_file_system/drive_backend/remote_to_local_syncer.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/remote_to_local_syncer.h"
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/format_macros.h"
 #include "base/location.h"
@@ skipping 653 matching lines @@
 void RemoteToLocalSyncer::DeleteLocalFile(const SyncStatusCallback& callback) {
   remote_change_processor()->ApplyRemoteChange(
       FileChange(FileChange::FILE_CHANGE_DELETE, SYNC_FILE_TYPE_UNKNOWN),
       base::FilePath(),
       url_,
       callback);
 }
 
 void RemoteToLocalSyncer::DownloadFile(const SyncStatusCallback& callback) {
   base::PostTaskAndReplyWithResult(
-      sync_context_->GetFileTaskRunner(), FROM_HERE,
+      sync_context_->GetBlockingTaskRunner(), FROM_HERE,
       base::Bind(&sync_file_system::drive_backend::CreateTemporaryFile,
-                 make_scoped_refptr(sync_context_->GetFileTaskRunner())),
+                 make_scoped_refptr(sync_context_->GetBlockingTaskRunner())),
       base::Bind(&RemoteToLocalSyncer::DidCreateTemporaryFileForDownload,
                  weak_ptr_factory_.GetWeakPtr(), callback));
 }
 
 void RemoteToLocalSyncer::DidCreateTemporaryFileForDownload(
     const SyncStatusCallback& callback,
     webkit_blob::ScopedFile file) {
   base::FilePath path = file.path();
   drive_service()->DownloadFile(
       path, remote_metadata_->file_id(),
       base::Bind(&RemoteToLocalSyncer::DidDownloadFile,
                  weak_ptr_factory_.GetWeakPtr(),
                  callback, base::Passed(&file)),
       google_apis::GetContentCallback(),
       google_apis::ProgressCallback());
 }
 
 void RemoteToLocalSyncer::DidDownloadFile(const SyncStatusCallback& callback,
                                           webkit_blob::ScopedFile file,
                                           google_apis::GDataErrorCode error,
                                           const base::FilePath&) {
   SyncStatusCode status = GDataErrorCodeToSyncStatusCode(error);
   if (status != SYNC_STATUS_OK) {
     callback.Run(status);
     return;
   }
 
   base::FilePath path = file.path();
   base::PostTaskAndReplyWithResult(
-      sync_context_->GetFileTaskRunner(), FROM_HERE,
+      sync_context_->GetBlockingTaskRunner(), FROM_HERE,
       base::Bind(&drive::util::GetMd5Digest, path),
       base::Bind(&RemoteToLocalSyncer::DidCalculateMD5ForDownload,
                  weak_ptr_factory_.GetWeakPtr(),
                  callback, base::Passed(&file)));
 }
 
 void RemoteToLocalSyncer::DidCalculateMD5ForDownload(
     const SyncStatusCallback& callback,
     webkit_blob::ScopedFile file,
     const std::string& md5) {
@@ skipping 45 matching lines @@
   return sync_context_->GetMetadataDatabase();
 }
 
 RemoteChangeProcessor* RemoteToLocalSyncer::remote_change_processor() {
   DCHECK(sync_context_->GetRemoteChangeProcessor());
   return sync_context_->GetRemoteChangeProcessor();
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system