Couple of fixes for DesktopWindowTreeHostMus.

ui/views/widget/desktop_aura/desktop_native_widget_aura.h

Index: ui/views/widget/desktop_aura/desktop_native_widget_aura.h
diff --git a/ui/views/widget/desktop_aura/desktop_native_widget_aura.h b/ui/views/widget/desktop_aura/desktop_native_widget_aura.h
index 8d7380826ca7cdc87cf56720ae9ffc1c8d5e98a7..bf8e667f8e4c7fe9f7dcba5bc600e56d83e84b6a 100644
--- a/ui/views/widget/desktop_aura/desktop_native_widget_aura.h
+++ b/ui/views/widget/desktop_aura/desktop_native_widget_aura.h
@@ -90,6 +90,8 @@ class VIEWS_EXPORT DesktopNativeWidgetAura
     return host_.get();
   }
 
+  aura::Window* content_window() { return content_window_; }
+
   // Ensures that the correct window is activated/deactivated based on whether
   // we are being activated/deactivated.
   void HandleActivationChanged(bool active);