Rename RootWindowHost* to WindowTreeHost*

ash/display/display_controller.cc

Index: ash/display/display_controller.cc
diff --git a/ash/display/display_controller.cc b/ash/display/display_controller.cc
index 09927b31c0901893c383dba83be500a20efb406e..6b479210320b01951dc276069b2badc341f2dc95 100644
--- a/ash/display/display_controller.cc
+++ b/ash/display/display_controller.cc
@@ -671,7 +671,7 @@ void DisplayController::OnDisplayRemoved(const gfx::Display& display) {
   base::MessageLoop::current()->DeleteSoon(FROM_HERE, controller);
 }
 
-void DisplayController::OnRootWindowHostResized(const aura::RootWindow* root) {
+void DisplayController::OnWindowTreeHostResized(const aura::RootWindow* root) {
   internal::DisplayManager* display_manager = GetDisplayManager();
   gfx::Display display = GetDisplayNearestWindow(root->window());
   if (display_manager->UpdateDisplayBounds(
@@ -757,7 +757,7 @@ aura::RootWindow* DisplayController::AddRootWindowForDisplay(
   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()->
-      CreateRootWindowHost(bounds_in_native);
+      CreateWindowTreeHost(bounds_in_native);
   aura::RootWindow* root_window = new aura::RootWindow(params);
   root_window->window()->SetName(
       base::StringPrintf("RootWindow-%d", root_window_count++));