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

ash/mus/screen_mus.cc

Index: ash/mus/screen_mus.cc
diff --git a/ash/mus/screen_mus.cc b/ash/mus/screen_mus.cc
index 312eb9d6505ed29473565263396008d7b88e35f9..f8c15862c0ab17dd8b14dcf8ce7d2f78ff3ba444 100644
--- a/ash/mus/screen_mus.cc
+++ b/ash/mus/screen_mus.cc
@@ -4,6 +4,7 @@
 
 #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"
 
@@ -23,4 +24,8 @@ display::Display ScreenMus::GetDisplayNearestWindow(
   return iter == display_list().displays().end() ? GetPrimaryDisplay() : *iter;
 }
 
+gfx::Point ScreenMus::GetCursorScreenPoint() {
+  return aura::Env::GetInstance()->last_mouse_location();
+}
+
 }  // namespace ash