Simplify calls for scale factor

ui/views/drag_utils.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/drag_utils.h"
 
-#include "ui/display/display.h"
-#include "ui/display/screen.h"
+#include "ui/base/layout.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/views/widget/widget.h"
 
 namespace views {
 
 float ScaleFactorForDragFromWidget(Widget* widget) {
   float device_scale = 1.0f;
   if (widget && widget->GetNativeView()) {
     gfx::NativeView view = widget->GetNativeView();
-    display::Display display =
-        display::Screen::GetScreen()->GetDisplayNearestWindow(view);
-    device_scale = display.device_scale_factor();
+    device_scale = ui::GetScaleFactorForNativeView(view);
   }
   return device_scale;
 }
 
 gfx::Canvas* GetCanvasForDragImage(Widget* widget,
                                    const gfx::Size& canvas_size) {
   float device_scale = ScaleFactorForDragFromWidget(widget);
   return new gfx::Canvas(canvas_size, device_scale, false);
 }
 
 }  // namespace views