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

ash/test/ash_test_base.cc

Index: ash/test/ash_test_base.cc
diff --git a/ash/test/ash_test_base.cc b/ash/test/ash_test_base.cc
index d03b281bfb19446218071638d3e4190ccea85c30..2dda31a48327cdf7921c1f832e7c33acc6e169b6 100644
--- a/ash/test/ash_test_base.cc
+++ b/ash/test/ash_test_base.cc
@@ -80,7 +80,8 @@ void AshTestBase::TearDown() {
 
 void AshTestBase::ChangeDisplayConfig(float scale,
                                       const gfx::Rect& bounds_in_pixel) {
-  gfx::Display display = gfx::Display(gfx::Screen::GetPrimaryDisplay().id());
+  gfx::Display display =
+      gfx::Display(Shell::GetAshScreen()->GetPrimaryDisplay().id());
   display.SetScaleAndBounds(scale, bounds_in_pixel);
   std::vector<gfx::Display> displays;
   displays.push_back(display);