Change webkit/{fileapi,quota} code to use TaskRunner.

webkit/fileapi/file_system_operation_context.cc

 // Copyright (c) 2012 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 "webkit/fileapi/file_system_operation_context.h"
 
 #include "webkit/fileapi/file_system_context.h"
 
 namespace fileapi {
 
 FileSystemOperationContext::FileSystemOperationContext(
     FileSystemContext* context)
     : file_system_context_(context),
       allowed_bytes_growth_(0) {}
 
 FileSystemOperationContext::~FileSystemOperationContext() {}
 
+base::SequencedTaskRunner*
+FileSystemOperationContext::file_task_runner() const {
+  return file_system_context_->file_task_runner();
+}
+
 }  // namespace fileapi