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

ash/wm/window_manager_unittest.cc

Index: ash/wm/window_manager_unittest.cc
diff --git a/ash/wm/window_manager_unittest.cc b/ash/wm/window_manager_unittest.cc
index b99bbb841bd58effd0fd5f40d0d4f4d425ea3843..b9155aee561e7a00c44cd4e44eb45de0d12c8902 100644
--- a/ash/wm/window_manager_unittest.cc
+++ b/ash/wm/window_manager_unittest.cc
@@ -464,9 +464,9 @@ TEST_F(WindowManagerTest, MouseEventCursors) {
 TEST_F(WindowManagerTest, MAYBE_TransformActivate) {
   aura::RootWindow* root_window = Shell::GetPrimaryRootWindow();
   gfx::Size size = root_window->bounds().size();
-  EXPECT_EQ(
-      gfx::Rect(size).ToString(),
-      gfx::Screen::GetDisplayNearestPoint(gfx::Point()).bounds().ToString());
+  EXPECT_EQ(gfx::Rect(size).ToString(),
+            Shell::GetScreen()->GetDisplayNearestPoint(
+                gfx::Point()).bounds().ToString());
 
   // Rotate it clock-wise 90 degrees.
   ui::Transform transform;