Rename RootWindowHost to WindowTreeHost

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 0b77ad8248bb545fa2d44cb1a59fccf450b5ef73..e5dd42afa20549ee29afd3abf64aa8d104629dda 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -92,7 +92,7 @@ class NestedDispatcherController;
 class NewWindowDelegate;
 class PartialMagnificationController;
 class PowerButtonController;
-class RootWindowHostFactory;
+class WindowTreeHostFactory;
 class ScreenAsh;
 class SessionStateDelegate;
 class Shelf;
@@ -499,7 +499,7 @@ class ASH_EXPORT Shell
     return resolution_notification_controller_.get();
   }
 
-  RootWindowHostFactory* root_window_host_factory() {
+  WindowTreeHostFactory* root_window_host_factory() {
     return root_window_host_factory_.get();
   }
 
@@ -643,7 +643,7 @@ class ASH_EXPORT Shell
   scoped_ptr<internal::EventClientImpl> event_client_;
   scoped_ptr<internal::EventTransformationHandler>
       event_transformation_handler_;
-  scoped_ptr<RootWindowHostFactory> root_window_host_factory_;
+  scoped_ptr<WindowTreeHostFactory> root_window_host_factory_;
 
   // An event filter that rewrites or drops an event.
   scoped_ptr<internal::EventRewriterEventFilter> event_rewriter_filter_;