ash/mash: Add a mus-client that sets up ash to provide the system ui for mash.

ui/views/mus/native_widget_mus.h

Index: ui/views/mus/native_widget_mus.h
diff --git a/ui/views/mus/native_widget_mus.h b/ui/views/mus/native_widget_mus.h
index caf889cc32059be756ff0da137ecf387ef388aec..57cb55c2c6884c2cf0edf8a5c9816604154017b8 100644
--- a/ui/views/mus/native_widget_mus.h
+++ b/ui/views/mus/native_widget_mus.h
@@ -23,6 +23,7 @@
 namespace aura {
 namespace client {
 class DefaultCaptureClient;
+class ScreenPositionClient;
 class WindowTreeClient;
 }
 class Window;
@@ -74,6 +75,8 @@ class VIEWS_MUS_EXPORT NativeWidgetMus : public internal::NativeWidgetPrivate,
 
   mus::Window* window() { return window_; }
 
+  aura::Window* GetRootWindow();
+
   void OnPlatformWindowClosed();
   void OnActivationChanged(bool active);
 
@@ -200,8 +203,6 @@ class VIEWS_MUS_EXPORT NativeWidgetMus : public internal::NativeWidgetPrivate,
  private:
   mus::Window* window_;
 
-  mojo::Shell* shell_;
-
   internal::NativeWidgetDelegate* native_widget_delegate_;
 
   const mus::mojom::SurfaceType surface_type_;
@@ -217,6 +218,7 @@ class VIEWS_MUS_EXPORT NativeWidgetMus : public internal::NativeWidgetPrivate,
   scoped_ptr<wm::FocusController> focus_client_;
   scoped_ptr<aura::client::DefaultCaptureClient> capture_client_;
   scoped_ptr<aura::client::WindowTreeClient> window_tree_client_;
+  scoped_ptr<aura::client::ScreenPositionClient> screen_position_client_;
   base::WeakPtrFactory<NativeWidgetMus> close_widget_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeWidgetMus);