Make OnWmDisplayRemoved() take a WindowTreeHost

ui/aura/mus/window_manager_delegate.h

 // Copyright 2015 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 UI_AURA_MUS_WINDOW_MANAGER_DELEGATE_H_
 #define UI_AURA_MUS_WINDOW_MANAGER_DELEGATE_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 95 matching lines @@
   virtual void OnWmClientJankinessChanged(
       const std::set<Window*>& client_windows,
       bool janky) = 0;
 
   // Called when a display is added. |window_tree_host| is the WindowTreeHost
   // for the new display.
   virtual void OnWmNewDisplay(
       std::unique_ptr<WindowTreeHostMus> window_tree_host,
       const display::Display& display) = 0;
 
-  // Called when a display is removed. |window| is the root of the display.
-  virtual void OnWmDisplayRemoved(Window* window) = 0;
+  // Called when a display is removed. |window_tree_host| is the WindowTreeHost
+  // for the display.
+  virtual void OnWmDisplayRemoved(WindowTreeHostMus* window_tree_host) = 0;
 
   // Called when a display is modified.
   virtual void OnWmDisplayModified(const display::Display& display) = 0;
 
   virtual ui::mojom::EventResult OnAccelerator(uint32_t id,
                                                const ui::Event& event);
 
   virtual void OnWmPerformMoveLoop(
       Window* window,
       ui::mojom::MoveLoopSource source,
       const gfx::Point& cursor_location,
       const base::Callback<void(bool)>& on_done) = 0;
 
   virtual void OnWmCancelMoveLoop(Window* window) = 0;
 
  protected:
   virtual ~WindowManagerDelegate() {}
 };
 
 }  // namespace ui
 
 #endif  // UI_AURA_MUS_WINDOW_MANAGER_DELEGATE_H_