Standardize Screen::GetCursorScreenPoint() on Env::last_mouse_location

ash/mus/screen_mus.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/mus/screen_mus.h"
 
+#include "ui/aura/env.h"
 #include "ui/aura/mus/window_tree_host_mus.h"
 #include "ui/aura/window.h"
 
 namespace ash {
 
 ScreenMus::ScreenMus() = default;
 
 ScreenMus::~ScreenMus() = default;
 
 display::Display ScreenMus::GetDisplayNearestWindow(
     aura::Window* window) const {
   const aura::WindowTreeHost* host = window->GetHost();
   if (!host)
     return GetPrimaryDisplay();
   auto iter = display_list().FindDisplayById(
       static_cast<const aura::WindowTreeHostMus*>(host)->display_id());
   return iter == display_list().displays().end() ? GetPrimaryDisplay() : *iter;
 }
 
+gfx::Point ScreenMus::GetCursorScreenPoint() {
+  return aura::Env::GetInstance()->last_mouse_location();
+}
+
 }  // namespace ash