Makes workspace 2 show an alternate background (system background)

ash/wm/workspace/system_background_controller.h

+// Copyright (c) 2012 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 ASH_WM_WORKSPACE_SYSTEM_BACKGROUND_CONTROLLER_H_
+#define ASH_WM_WORKSPACE_SYSTEM_BACKGROUND_CONTROLLER_H_
+
+#include "ash/ash_export.h"
+#include "base/basictypes.h"
+
+namespace aura {
+class RootWindow;
+};
+
+namespace ash {
+namespace internal {
+
+// SystemBackgroundController shows the system level background.

[Ben Goodger (Google), 2012/08/27 15:50:47]

Maybe explain here too what a system background is.

+class ASH_EXPORT SystemBackgroundController {
+ public:
+  explicit SystemBackgroundController(aura::RootWindow* root);
+  ~SystemBackgroundController();
+
+ private:
+  class View;
+
+  // View responsible for rendering the background. This is non-NULL if the
+  // widget containing it is deleted. It is owned by the widget.
+  View* view_;
+
+  DISALLOW_COPY_AND_ASSIGN(SystemBackgroundController);
+};
+
+}  // namespace internal
+}  // namespace ash
+
+#endif  // ASH_WM_WORKSPACE_SYSTEM_BACKGROUND_CONTROLLER_H_