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

athena/screen/public/screen_manager.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_PUBLIC_SCREEN_MANAGER_H_
+#define ATHENA_SCREEN_PUBLIC_SCREEN_MANAGER_H_
+
+#include "athena/athena_export.h"
+
+namespace aura {
+class Window;
+}
+
+namespace gfx {
+class ImageSkia;
+}
+
+namespace athena {
+
+// Mananges screen and UI components on the screen such as background,
+// home card, etc.
+class ATHENA_EXPORT ScreenManager {
+ public:
+  // Creates, returns and deletes the singleton object of the ScreenManager
+  // implementation.
+  static ScreenManager* Create(aura::Window* root);
+  static ScreenManager* Get();
+  static void Shutdown();
+
+  virtual ~ScreenManager() {}
+
+  // Returns the container window for window on the screen.
+  virtual aura::Window* GetContainerWindow() = 0;
+
+  // Return the context object to be used for widget creation.
+  virtual aura::Window* GetContext() = 0;
+
+  // Sets the background image.
+  virtual void SetBackgroundImage(const gfx::ImageSkia& image) = 0;
+};
+
+}  // namespace athena
+
+#endif  // ATHENA_SCREEN_PUBLIC_SCREEN_MANAGER_H_