Add context to gfx::Screen calls in support of simultaneous desktop+ash

ash/wm/window_util.cc

Index: ash/wm/window_util.cc
diff --git a/ash/wm/window_util.cc b/ash/wm/window_util.cc
index 74c970f631ac85b13238c3bb52e1a8e537617d2c..3260a69ac64c761ae9cfd09c2a8ba0ef65aaafbb 100644
--- a/ash/wm/window_util.cc
+++ b/ash/wm/window_util.cc
@@ -101,7 +101,8 @@ void RestoreWindow(aura::Window* window) {
 }
 
 void CenterWindow(aura::Window* window) {
-  const gfx::Display display = gfx::Screen::GetDisplayNearestWindow(window);
+  const gfx::Display display =
+      Shell::GetAshScreen()->GetDisplayNearestWindow(window);
   gfx::Rect center = display.work_area().Center(window->bounds().size());
   window->SetBounds(center);
 }