Remove now-unnecessary wrappers around gfx::Screen::GetScreen()

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 9503fd448c02605415238f18d372f80dc709c3b0..2c146a8aa294a1ed18d8ab7c4e29f276bdf02ef5 100644
--- a/ash/display/screen_position_controller.cc
+++ b/ash/display/screen_position_controller.cc
@@ -123,8 +123,11 @@ void ScreenPositionController::ConvertPointToScreen(
     gfx::Point* point) {
   const aura::Window* root = window->GetRootWindow();
   aura::Window::ConvertPointToTarget(window, root, point);
-  const gfx::Point display_origin = Shell::GetScreen()->GetDisplayNearestWindow(
-      const_cast<aura::Window*>(root)).bounds().origin();
+  const gfx::Point display_origin =
+      gfx::Screen::GetScreen()
+          ->GetDisplayNearestWindow(const_cast<aura::Window*>(root))
+          .bounds()
+          .origin();
   point->Offset(display_origin.x(), display_origin.y());
 }
 
@@ -132,8 +135,11 @@ void ScreenPositionController::ConvertPointFromScreen(
     const aura::Window* window,
     gfx::Point* point) {
   const aura::Window* root = window->GetRootWindow();
-  const gfx::Point display_origin = Shell::GetScreen()->GetDisplayNearestWindow(
-      const_cast<aura::Window*>(root)).bounds().origin();
+  const gfx::Point display_origin =
+      gfx::Screen::GetScreen()
+          ->GetDisplayNearestWindow(const_cast<aura::Window*>(root))
+          .bounds()
+          .origin();
   point->Offset(-display_origin.x(), -display_origin.y());
   aura::Window::ConvertPointToTarget(root, window, point);
 }
@@ -222,8 +228,10 @@ void ScreenPositionController::SetBounds(aura::Window* window,
     }
   }
   gfx::Point origin(bounds.origin());
-  const gfx::Point display_origin = Shell::GetScreen()->GetDisplayNearestWindow(
-      window).bounds().origin();
+  const gfx::Point display_origin = gfx::Screen::GetScreen()
+                                        ->GetDisplayNearestWindow(window)
+                                        .bounds()
+                                        .origin();
   origin.Offset(-display_origin.x(), -display_origin.y());
   window->SetBounds(gfx::Rect(origin, bounds.size()));
 }