Make GetRootWindow() return a Window instead of a RootWindow.

ui/views/widget/desktop_aura/desktop_screen_x11.cc

Index: ui/views/widget/desktop_aura/desktop_screen_x11.cc
diff --git a/ui/views/widget/desktop_aura/desktop_screen_x11.cc b/ui/views/widget/desktop_aura/desktop_screen_x11.cc
index 9358875895ac0bd2f1aadb30c27df4f1fd018773..8d8bd02ee8311ee6be0c50efcaf369ed7d1c4651 100644
--- a/ui/views/widget/desktop_aura/desktop_screen_x11.cc
+++ b/ui/views/widget/desktop_aura/desktop_screen_x11.cc
@@ -187,10 +187,10 @@ gfx::Display DesktopScreenX11::GetDisplayNearestWindow(
   // create the aura::RootWindow. So we ask what the DRWHX11 believes the
   // window bounds are instead of going through the aura::Window's screen
   // bounds.
-  aura::RootWindow* root_window = window->GetRootWindow();
-  if (root_window) {
+  aura::WindowEventDispatcher* dispatcher = window->GetDispatcher();
+  if (dispatcher) {
     DesktopRootWindowHostX11* rwh = DesktopRootWindowHostX11::GetHostForXID(
-        root_window->GetAcceleratedWidget());
+        dispatcher->GetAcceleratedWidget());
     if (rwh)
       return GetDisplayMatching(rwh->GetX11RootWindowBounds());
   }