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

ash/display/screen_position_controller.cc

Index: ash/display/screen_position_controller.cc
diff --git a/ash/display/screen_position_controller.cc b/ash/display/screen_position_controller.cc
index 3f2c39200cbf24c4a70f67a7536f268b23e38c54..791ecce419b9927240f3c2cc38e161b999a456f3 100644
--- a/ash/display/screen_position_controller.cc
+++ b/ash/display/screen_position_controller.cc
@@ -61,9 +61,8 @@ void ScreenPositionController::ConvertPointToScreen(
     gfx::Point* point) {
   const aura::RootWindow* root = window->GetRootWindow();
   aura::Window::ConvertPointToTarget(window, root, point);
-  const gfx::Point display_origin =
-      gfx::Screen::GetDisplayNearestWindow(
-          const_cast<aura::RootWindow*>(root)).bounds().origin();
+  const gfx::Point display_origin = Shell::GetScreen()->GetDisplayNearestWindow(
+      const_cast<aura::RootWindow*>(root)).bounds().origin();
   point->Offset(display_origin.x(), display_origin.y());
 }
 
@@ -71,9 +70,8 @@ void ScreenPositionController::ConvertPointFromScreen(
     const aura::Window* window,
     gfx::Point* point) {
   const aura::RootWindow* root = window->GetRootWindow();
-  const gfx::Point display_origin =
-      gfx::Screen::GetDisplayNearestWindow(
-          const_cast<aura::RootWindow*>(root)).bounds().origin();
+  const gfx::Point display_origin = Shell::GetScreen()->GetDisplayNearestWindow(
+      const_cast<aura::RootWindow*>(root)).bounds().origin();
   point->Offset(-display_origin.x(), -display_origin.y());
   aura::Window::ConvertPointToTarget(root, window, point);
 }
@@ -150,8 +148,8 @@ void ScreenPositionController::SetBounds(aura::Window* window,
   }
 
   gfx::Point origin(bounds.origin());
-  const gfx::Point display_origin =
-      gfx::Screen::GetDisplayNearestWindow(window).bounds().origin();
+  const gfx::Point display_origin = Shell::GetScreen()->GetDisplayNearestWindow(
+      window).bounds().origin();
   origin.Offset(-display_origin.x(), -display_origin.y());
   window->SetBounds(gfx::Rect(origin, bounds.size()));
 }