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

ui/aura/test/test_screen.cc

Index: ui/aura/test/test_screen.cc
diff --git a/ui/aura/test/test_screen.cc b/ui/aura/test/test_screen.cc
index b3aaf949314382af619a9826ef710eb0ab28d689..8aa41663fc2429c90dedd324e47ed496a7baf8e2 100644
--- a/ui/aura/test/test_screen.cc
+++ b/ui/aura/test/test_screen.cc
@@ -20,12 +20,16 @@ TestScreen::TestScreen(aura::RootWindow* root_window)
 TestScreen::~TestScreen() {
 }
 
+bool TestScreen::IsDIPEnabled() {
+  return true;
+}
+
 gfx::Point TestScreen::GetCursorScreenPoint() {
   return Env::GetInstance()->last_mouse_location();
 }
 
 gfx::NativeWindow TestScreen::GetWindowAtCursorScreenPoint() {
-  const gfx::Point point = gfx::Screen::GetCursorScreenPoint();
+  const gfx::Point point = GetCursorScreenPoint();
   return root_window_->GetTopWindowContainingPoint(point);
 }