Rename RootWindowHost* to WindowTreeHost*

ui/views/widget/desktop_aura/x11_desktop_handler.cc

Index: ui/views/widget/desktop_aura/x11_desktop_handler.cc
diff --git a/ui/views/widget/desktop_aura/x11_desktop_handler.cc b/ui/views/widget/desktop_aura/x11_desktop_handler.cc
index 0cfe040cbdfb952689f02c098c91d6f33024d932..3a14e04c076cebcbace6271db290e940ef144ef7 100644
--- a/ui/views/widget/desktop_aura/x11_desktop_handler.cc
+++ b/ui/views/widget/desktop_aura/x11_desktop_handler.cc
@@ -151,13 +151,13 @@ void X11DesktopHandler::OnWillDestroyEnv() {
 void X11DesktopHandler::OnActiveWindowChanged(::Window xid) {
   if (current_window_ == xid)
     return;
-  DesktopRootWindowHostX11* old_host =
-      views::DesktopRootWindowHostX11::GetHostForXID(current_window_);
+  DesktopWindowTreeHostX11* old_host =
+      views::DesktopWindowTreeHostX11::GetHostForXID(current_window_);
   if (old_host)
     old_host->HandleNativeWidgetActivationChanged(false);
 
-  DesktopRootWindowHostX11* new_host =
-      views::DesktopRootWindowHostX11::GetHostForXID(xid);
+  DesktopWindowTreeHostX11* new_host =
+      views::DesktopWindowTreeHostX11::GetHostForXID(xid);
   if (new_host)
     new_host->HandleNativeWidgetActivationChanged(true);