Removes some dead code

ash/mus/bridge/wm_root_window_controller_mus.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_MUS_BRIDGE_WM_ROOT_WINDOW_CONTROLLER_MUS_H_
 #define ASH_MUS_BRIDGE_WM_ROOT_WINDOW_CONTROLLER_MUS_H_
 
 #include "ash/common/wm_root_window_controller.h"
 #include "base/macros.h"
 
@@ skipping 25 matching lines @@
   }
   static const WmRootWindowControllerMus* Get(const aura::Window* window);
 
   RootWindowController* root_window_controller() {
     return root_window_controller_;
   }
 
   // Screen conversion functions.
   gfx::Point ConvertPointToScreen(const WmWindowMus* source,
                                   const gfx::Point& point) const;
-  gfx::Point ConvertPointFromScreen(const WmWindowMus* target,
-                                    const gfx::Point& point) const;
 
   const display::Display& GetDisplay() const;
 
   // Exposed as public so WindowManager can call it.
   void MoveWindowsTo(WmWindow* dest);
 
   // WmRootWindowController:
   bool HasShelf() override;
   WmShell* GetShell() override;
   WmShelf* GetShelf() override;
@@ skipping 14 matching lines @@
   WmShellMus* shell_;
   RootWindowController* root_window_controller_;
 
   DISALLOW_COPY_AND_ASSIGN(WmRootWindowControllerMus);
 };
 
 }  // namespace mus
 }  // namespace ash
 
 #endif  // ASH_MUS_BRIDGE_WM_ROOT_WINDOW_CONTROLLER_MUS_H_