ash: Remove wm::GetRootWindowController.

ash/wm/window_util.cc

Index: ash/wm/window_util.cc
diff --git a/ash/wm/window_util.cc b/ash/wm/window_util.cc
index 5e9f37a00985b5f3ba04fe716570801659e45212..0b71f068d51ab604660ca1153b99605585f1563f 100644
--- a/ash/wm/window_util.cc
+++ b/ash/wm/window_util.cc
@@ -59,11 +59,6 @@ bool CanActivateWindow(aura::Window* window) {
   return client && client->CanActivateWindow(window);
 }
 
-internal::RootWindowController* GetRootWindowController(
-    aura::RootWindow* root_window) {
-  return root_window->GetProperty(internal::kRootWindowControllerKey);
-}
-
 bool IsWindowNormal(aura::Window* window) {
   return window->GetProperty(aura::client::kShowStateKey) ==
           ui::SHOW_STATE_NORMAL ||