Revert 219983 "Work-around fix for SyncFS file upload"

trunk/src/chrome/browser/sync_file_system/drive_backend/api_util.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/api_util.h"
 
 #include <algorithm>
 #include <functional>
 #include <sstream>
 #include <string>
@@ skipping 891 matching lines @@
   }
 
   std::string mime_type = GetMimeTypeFromTitle(entry->title());
   UploadKey upload_key = RegisterUploadCallback(callback);
   ResourceEntryCallback did_upload_callback =
       base::Bind(&APIUtil::DidUploadExistingFile, AsWeakPtr(), upload_key);
   drive_uploader_->UploadExistingFile(
       entry->resource_id(),
       local_file_path,
       mime_type,
-      // Don't use etag for uploading for now. http://crbug.com/278201
-      std::string(), // entry->etag(),
+      entry->etag(),
       base::Bind(&UploadResultAdapter, did_upload_callback),
       google_apis::ProgressCallback());
 }
 
 bool APIUtil::IsAuthenticated() const {
   return drive_service_->HasRefreshToken();
 }
 
 void APIUtil::DidUploadExistingFile(
     UploadKey upload_key,
@@ skipping 215 matching lines @@
 }
 
 std::string APIUtil::GetRootResourceId() const {
   if (IsDriveAPIDisabled())
     return drive_service_->GetRootResourceId();
   return root_resource_id_;
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system