Nix GetRootWindowController, use RootWindowController::ForWindow.

ash/wm_window.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/wm_window.h"
 
 #include "ash/ash_constants.h"
 #include "ash/public/cpp/config.h"
 #include "ash/public/cpp/shell_window_ids.h"
 #include "ash/public/cpp/window_properties.h"
-#include "ash/root_window_controller.h"
 #include "ash/shell.h"
 #include "ash/wm/resize_handle_window_targeter.h"
 #include "ash/wm/widget_finder.h"
 #include "ash/wm/window_animations.h"
 #include "ash/wm/window_properties.h"
 #include "ash/wm/window_state.h"
 #include "ash/wm/window_util.h"
 #include "ash/wm_transient_window_observer.h"
 #include "base/memory/ptr_util.h"
 #include "services/ui/public/interfaces/window_manager_constants.mojom.h"
@@ skipping 77 matching lines @@
 
 void WmWindow::Destroy() {
   delete window_;
   // WARNING: this has been deleted.
 }
 
 const WmWindow* WmWindow::GetRootWindow() const {
   return Get(window_->GetRootWindow());
 }
 
-RootWindowController* WmWindow::GetRootWindowController() {
-  aura::Window* root = window_->GetRootWindow();
-  return root ? RootWindowController::ForWindow(root) : nullptr;
-}
-
 aura::client::WindowType WmWindow::GetType() const {
   return window_->type();
 }
 
 int WmWindow::GetAppType() const {
   return window_->GetProperty(aura::client::kAppType);
 }
 
 void WmWindow::SetAppType(int app_type) const {
   window_->SetProperty(aura::client::kAppType, app_type);
@@ skipping 406 matching lines @@
     observer.OnTransientChildAdded(this, Get(transient));
 }
 
 void WmWindow::OnTransientChildRemoved(aura::Window* window,
                                        aura::Window* transient) {
   for (auto& observer : transient_observers_)
     observer.OnTransientChildRemoved(this, Get(transient));
 }
 
 }  // namespace ash