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

ui/aura/test/aura_test_helper.cc

Index: ui/aura/test/aura_test_helper.cc
diff --git a/ui/aura/test/aura_test_helper.cc b/ui/aura/test/aura_test_helper.cc
index 1453c867027b294664fed55b08e5d136e0349ca3..0b90c201f213cc63e3eb631477d725cf7e19be06 100644
--- a/ui/aura/test/aura_test_helper.cc
+++ b/ui/aura/test/aura_test_helper.cc
@@ -46,7 +46,8 @@ void AuraTestHelper::SetUp() {
   setup_called_ = true;
   Env::GetInstance()->SetDisplayManager(new SingleDisplayManager);
   root_window_.reset(aura::DisplayManager::CreateRootWindowForPrimaryDisplay());
-  gfx::Screen::SetInstance(new aura::TestScreen(root_window_.get()));
+  gfx::Screen::SetScreenInstance(
+      gfx::SCREEN_TYPE_NATIVE, new aura::TestScreen(root_window_.get()));
   ui_controls::InstallUIControlsAura(CreateUIControlsAura(root_window_.get()));
 
   focus_manager_.reset(new FocusManager);