Makes sure bounds and visibilty are updated correctly for new displays

ui/aura/mus/window_tree_client.h

Index: ui/aura/mus/window_tree_client.h
diff --git a/ui/aura/mus/window_tree_client.h b/ui/aura/mus/window_tree_client.h
index 356f05812d09b07a34f62a1624952fa80504139b..407fc191ff57e2628d73552aef60fd5e9ffb7751 100644
--- a/ui/aura/mus/window_tree_client.h
+++ b/ui/aura/mus/window_tree_client.h
@@ -57,7 +57,6 @@ struct WindowPortPropertyData;
 class WindowTreeClientDelegate;
 class WindowTreeClientPrivate;
 class WindowTreeClientObserver;
-class WindowTreeHost;
 class WindowTreeHostMus;
 
 namespace client {
@@ -238,9 +237,9 @@ class AURA_EXPORT WindowTreeClient
                    bool drawn);
 
   // Called by WmNewDisplayAdded().
-  WindowTreeHost* WmNewDisplayAddedImpl(const display::Display& display,
-                                        ui::mojom::WindowDataPtr root_data,
-                                        bool parent_drawn);
+  WindowTreeHostMus* WmNewDisplayAddedImpl(const display::Display& display,
+                                           ui::mojom::WindowDataPtr root_data,
+                                           bool parent_drawn);
 
   std::unique_ptr<EventResultCallback> CreateEventResultCallback(
       int32_t event_id);