Move root_window_host* in aura to window_tree_host*.

ash/display/virtual_keyboard_window_controller.cc

Index: ash/display/virtual_keyboard_window_controller.cc
diff --git a/ash/display/virtual_keyboard_window_controller.cc b/ash/display/virtual_keyboard_window_controller.cc
index f1ac8aaccf5ba695de697039969f2b0d8a1e809e..bdd9cdb35525c5366c73b1c7dad79e02c658807b 100644
--- a/ash/display/virtual_keyboard_window_controller.cc
+++ b/ash/display/virtual_keyboard_window_controller.cc
@@ -8,7 +8,7 @@
 #include "ash/display/display_info.h"
 #include "ash/display/display_manager.h"
 #include "ash/display/root_window_transformers.h"
-#include "ash/host/root_window_host_factory.h"
+#include "ash/host/window_tree_host_factory.h"
 #include "ash/root_window_controller.h"
 #include "ash/root_window_settings.h"
 #include "ash/shell.h"
@@ -42,7 +42,7 @@ void VirtualKeyboardWindowController::UpdateWindow(
   if (!root_window_controller_.get()) {
     const gfx::Rect& bounds_in_native = display_info.bounds_in_native();
     aura::RootWindow::CreateParams params(bounds_in_native);
-    params.host = Shell::GetInstance()->root_window_host_factory()->
+    params.host = Shell::GetInstance()->window_tree_host_factory()->
         CreateWindowTreeHost(bounds_in_native);
     aura::RootWindow* root_window = new aura::RootWindow(params);