Remove PrepareForShutdown

ui/aura/window_tree_host_ozone.cc

 // Copyright 2013 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 "ui/aura/window_tree_host_ozone.h"
 
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/base/cursor/ozone/cursor_factory_ozone.h"
 #include "ui/events/ozone/event_factory_ozone.h"
 #include "ui/gfx/ozone/surface_factory_ozone.h"
@@ skipping 78 matching lines @@
 void WindowTreeHostOzone::PostNativeEvent(
     const base::NativeEvent& native_event) {
   NOTIMPLEMENTED();
 }
 
 void WindowTreeHostOzone::OnDeviceScaleFactorChanged(
     float device_scale_factor) {
   NOTIMPLEMENTED();
 }
 
-void WindowTreeHostOzone::PrepareForShutdown() { NOTIMPLEMENTED(); }
-
 void WindowTreeHostOzone::SetCursorNative(gfx::NativeCursor cursor) {
   ui::CursorFactoryOzone::GetInstance()->SetCursor(GetAcceleratedWidget(),
                                                    cursor.platform());
 }
 
 void WindowTreeHostOzone::MoveCursorToNative(const gfx::Point& location) {
   ui::EventFactoryOzone::GetInstance()->WarpCursorTo(GetAcceleratedWidget(),
                                                      location);
 }
 
@@ skipping 10 matching lines @@
   return new WindowTreeHostOzone(bounds);
 }
 
 // static
 gfx::Size WindowTreeHost::GetNativeScreenSize() {
   NOTIMPLEMENTED();
   return gfx::Size();
 }
 
 }  // namespace aura