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

ui/views/mus/window_manager_connection.h

Index: ui/views/mus/window_manager_connection.h
diff --git a/ui/views/mus/window_manager_connection.h b/ui/views/mus/window_manager_connection.h
index 610cbf50c3151501140649e8fd150c421c106273..b55f9310b6ea871faf4edcf81731b853798f0c10 100644
--- a/ui/views/mus/window_manager_connection.h
+++ b/ui/views/mus/window_manager_connection.h
@@ -45,6 +45,9 @@ class VIEWS_MUS_EXPORT WindowManagerConnection
   mus::Window* NewWindow(const std::map<std::string,
                          std::vector<uint8_t>>& properties);
 
+  NativeWidget* CreateNativeWidgetMus(const Widget::InitParams& init_params,
+                                      internal::NativeWidgetDelegate* delegate);
+
  private:
   explicit WindowManagerConnection(mojo::ApplicationImpl* app);
   ~WindowManagerConnection() override;
@@ -56,9 +59,6 @@ class VIEWS_MUS_EXPORT WindowManagerConnection
   // ScreenMusDelegate:
   void OnWindowManagerFrameValuesChanged() override;
 
-  NativeWidget* CreateNativeWidget(const Widget::InitParams& init_params,
-                                   internal::NativeWidgetDelegate* delegate);
-
   mojo::ApplicationImpl* app_;
   scoped_ptr<ScreenMus> screen_;
   scoped_ptr<mus::WindowTreeConnection> window_tree_connection_;