[Athena] minimum impl to add screen/background and test windows

athena/screen/background_controller.h

+// Copyright 2014 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 ATHENA_SCREEN_BACKGROUND_CONTROLLER_H_
+#define ATHENA_SCREEN_BACKGROUND_CONTROLLER_H_
+
+#include "base/macros.h"
+
+namespace aura {
+class Window;
+}
+
+namespace gfx {
+class ImageSkia;
+}
+
+namespace athena {
+class BackgroundView;
+
+// Controls background image switching.
+class BackgroundController {
+ public:
+  explicit BackgroundController(aura::Window* container);
+  ~BackgroundController();
+
+  void SetImage(const gfx::ImageSkia& image);
+
+ private:
+  BackgroundView* background_view_;
+
+  DISALLOW_COPY_AND_ASSIGN(BackgroundController);
+};
+}
+
+#endif  // ATHENA_SCREEN_BACKGROUND_CONTROLLER_H_