Adding an IO Data and keyed service to previews/

components/previews/previews_io_data.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_IO_DATA_H_
+#define COMPONENTS_PREVIEWS_PREVIEWS_IO_DATA_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 PreviewsUIService;
+
+// A class to manage the IO portion of inter-thread communication between
+// previews/ objects. Created on the UI thread, but used only on the IO thread
+// after initialization.
+class PreviewsIOData {
+ public:
+  PreviewsIOData(
+      const scoped_refptr<base::SingleThreadTaskRunner>& ui_task_runner,
+      const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner);
+  virtual ~PreviewsIOData();
+
+  // Stores |previews_ui_service| as |previews_ui_service_| and posts a task to
+  // InitializeOnIOThread on the IO thread.
+  void Initialize(base::WeakPtr<PreviewsUIService> previews_ui_service);
+
+ protected:
+  // Posts a task to SetIOData for |previews_ui_service_| on the UI thread with
+  // a weak pointer to |this|. Virtualized for testing.
+  virtual void InitializeOnIOThread();
+
+ private:
+  // The UI thread portion of the inter-thread communication for previews.
+  base::WeakPtr<PreviewsUIService> previews_ui_service_;
+
+  // The UI and IO thread task runners. |ui_task_runner_| is used to post
+  // tasks to |previews_ui_service_|, and |io_task_runner_| is used to post from
+  // Initialize to InitializeOnIOThread as well as verify that execution is
+  // happening on the IO thread.
+  scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner_;
+  scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
+
+  base::WeakPtrFactory<PreviewsIOData> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(PreviewsIOData);
+};
+
+}  // namespace previews
+
+#endif  // COMPONENTS_PREVIEWS_PREVIEWS_IO_DATA_H_