Changed previews component to be a layered component.

components/previews/previews_ui_service.h

-// Copyright 2016 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.
-
-#ifndef COMPONENTS_PREVIEWS_PREVIEWS_UI_SERVICE_H_
-#define COMPONENTS_PREVIEWS_PREVIEWS_UI_SERVICE_H_
-
-#include <string>
-
-#include "base/macros.h"
-#include "base/memory/ref_counted.h"
-#include "base/memory/weak_ptr.h"
-#include "base/single_thread_task_runner.h"
-#include "base/threading/thread_checker.h"
-
-namespace previews {
-class PreviewsIOData;
-
-// A class to manage the UI portion of inter-thread communication between
-// previews/ objects. Created and used on the UI thread.
-class PreviewsUIService {
- public:
-  PreviewsUIService(
-      PreviewsIOData* previews_io_data,
-      const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner);
-  virtual ~PreviewsUIService();
-
-  // Sets |io_data_| to |io_data| to allow calls from the UI thread to the IO
-  // thread. Virtualized in testing.
-  virtual void SetIOData(base::WeakPtr<PreviewsIOData> io_data);
-
- private:
-  // The IO thread portion of the inter-thread communication for previews/.
-  base::WeakPtr<previews::PreviewsIOData> io_data_;
-
-  base::ThreadChecker thread_checker_;
-
-  // The IO thread task runner. Used to post tasks to |io_data_|.
-  scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
-
-  base::WeakPtrFactory<PreviewsUIService> weak_factory_;
-
-  DISALLOW_COPY_AND_ASSIGN(PreviewsUIService);
-};
-
-}  // namespace previews
-
-#endif  // COMPONENTS_PREVIEWS_PREVIEWS_UI_SERVICE_H_