[Athena] Add status icons and system time to the desktop background

athena/system/public/system_ui.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_SYSTEM_PUBLIC_SYSTEM_UI_H_
 #define ATHENA_SYSTEM_PUBLIC_SYSTEM_UI_H_
 
 #include "athena/athena_export.h"
 #include "base/memory/ref_counted.h"
 
 namespace base {
 class TaskRunner;
 }
 
+namespace gfx {
+class ImageSkia;
+}
+
+namespace views {
+class View;
+}
+
 namespace athena {
 
 class ATHENA_EXPORT SystemUI {
  public:
   // Creates and deletes the singleton object of the SystemUI implementation.
   static SystemUI* Create(scoped_refptr<base::TaskRunner> io_task_runner);
+  static SystemUI* Get();
   static void Shutdown();
 
   virtual ~SystemUI() {}
+
+  // Sets the background image.
+  virtual void SetBackgroundImage(const gfx::ImageSkia& image) = 0;
+
+  // Creates a view which displays the time.
+  virtual views::View* CreateTimeView() = 0;
+
+  // Creates a view which displays status icons and debug information.
+  virtual views::View* CreateStatusIconView() = 0;
 };
 
 }  // namespace athena
 
 #endif  // ATHENA_SYSTEM_PUBLIC_SYSTEM_UI_H_