Nix GetRootWindowController, use RootWindowController::ForWindow.

ash/wm_window.h

 // 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.
 
 #ifndef ASH_WM_WINDOW_H_
 #define ASH_WM_WINDOW_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 18 matching lines @@
 class Size;
 class Transform;
 }
 
 namespace ui {
 class Layer;
 }
 
 namespace ash {
 
-class RootWindowController;
 class WmTransientWindowObserver;
 enum class WmWindowProperty;
 
 namespace wm {
 class WindowState;
 }
 
 // WmWindow abstracts away differences between ash running in classic mode
 // and ash running with aura-mus.
 //
@@ skipping 36 matching lines @@
   aura::Window* aura_window() { return window_; }
   const aura::Window* aura_window() const { return window_; }
 
   void Destroy();
 
   WmWindow* GetRootWindow() {
     return const_cast<WmWindow*>(
         const_cast<const WmWindow*>(this)->GetRootWindow());
   }
   const WmWindow* GetRootWindow() const;
-  RootWindowController* GetRootWindowController();
 
   // See shell_window_ids.h for list of known ids.
   WmWindow* GetChildByShellWindowId(int id);
 
   aura::client::WindowType GetType() const;
   int GetAppType() const;
   void SetAppType(int app_type) const;
 
   ui::Layer* GetLayer();
 
@@ skipping 179 matching lines @@
 
   bool added_transient_observer_ = false;
   base::ObserverList<WmTransientWindowObserver> transient_observers_;
 
   DISALLOW_COPY_AND_ASSIGN(WmWindow);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_WINDOW_H_