Folds WmRootWindowController into RootWindowController

ash/mus/bridge/wm_window_mus.cc

Index: ash/mus/bridge/wm_window_mus.cc
diff --git a/ash/mus/bridge/wm_window_mus.cc b/ash/mus/bridge/wm_window_mus.cc
index 324c31ebcf6d83ca208817274ed18bfbcb6f24c0..ce54cc3b15d50e8322ac977064ccc401dbd7bd3e 100644
--- a/ash/mus/bridge/wm_window_mus.cc
+++ b/ash/mus/bridge/wm_window_mus.cc
@@ -61,10 +61,9 @@ bool WmWindowMus::IsContainer() const {
   return GetShellWindowId() != kShellWindowId_Invalid;
 }
 
-WmRootWindowController* WmWindowMus::GetRootWindowController() {
+ash::RootWindowController* WmWindowMus::GetRootWindowController() {
   return RootWindowController::ForWindow(aura_window())
-      ->ash_root_window_controller()
-      ->wm_root_window_controller();
+      ->ash_root_window_controller();
 }
 
 WmShell* WmWindowMus::GetShell() const {