Converts WindowTreeClientTest to be in terms of aura

ui/views/mus/desktop_window_tree_host_mus.h

Index: ui/views/mus/desktop_window_tree_host_mus.h
diff --git a/ui/views/mus/desktop_window_tree_host_mus.h b/ui/views/mus/desktop_window_tree_host_mus.h
index b988aeee1884761830bb0933c8d70d24d61504bc..a4cd22163cc48e562a0058baec7a35cad370048c 100644
--- a/ui/views/mus/desktop_window_tree_host_mus.h
+++ b/ui/views/mus/desktop_window_tree_host_mus.h
@@ -34,6 +34,9 @@ class VIEWS_MUS_EXPORT DesktopWindowTreeHostMus
       const std::map<std::string, std::vector<uint8_t>>* mus_properties);
   ~DesktopWindowTreeHostMus() override;
 
+  // Called when the window was deleted on the server.
+  void ServerDestroyedWindow() { CloseNow(); }
+
  private:
   bool IsDocked() const;