ash: Add RootWindowHostFactory class.

ash/host/root_window_host_factory.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_HOST_ROOT_WINDOW_HOST_FACTORY_H_
+#define ASH_HOST_ROOT_WINDOW_HOST_FACTORY_H_
+
+#include "ash/ash_export.h"
+#include "ui/gfx/rect.h"
+
+namespace aura {
+class RootWindowHost;
+}
+
+namespace ash {
+
+class ASH_EXPORT RootWindowHostFactory {
+ public:
+  virtual ~RootWindowHostFactory() {}
+
+  static RootWindowHostFactory* Create();
+
+  // Creates a new aura::RootWindowHost. The caller owns the returned value.
+  virtual aura::RootWindowHost* CreateRootWindowHost(
+      const gfx::Rect& initial_bounds) = 0;
+
+ protected:
+  RootWindowHostFactory() {}
+};
+
+}  // namespace ash
+
+#endif  // ASH_HOST_ROOT_WINDOW_HOST_FACTORY_H_