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

chrome/browser/ui/ash/window_positioner.cc

Index: chrome/browser/ui/ash/window_positioner.cc
diff --git a/chrome/browser/ui/ash/window_positioner.cc b/chrome/browser/ui/ash/window_positioner.cc
index e2e196871ee196b1d2cb9f6e94b6b2b271b9e6f7..853341954117b75b4a9c43241a3c4a8f7cfe3ef5 100644
--- a/chrome/browser/ui/ash/window_positioner.cc
+++ b/chrome/browser/ui/ash/window_positioner.cc
@@ -47,8 +47,8 @@ gfx::Rect WindowPositioner::GetPopupPosition(const gfx::Rect& old_pos) {
   // work area.
   aura::Window* window = ash::wm::GetActiveWindow();
   const gfx::Rect work_area = window && window->IsVisible() ?
-      gfx::Screen::GetDisplayNearestWindow(window).work_area() :
-      gfx::Screen::GetPrimaryDisplay().work_area();
+      Shell::GetScreen()->GetDisplayNearestWindow(window).work_area() :
+      Shell::GetScreen()->GetPrimaryDisplay().work_area();
   // Only try to reposition the popup when it is not spanning the entire
   // screen.
   if ((old_pos.width() + popup_position_offset_from_screen_corner_x >=