Use actual value of display scale factor from GetMonitorScaleFactor().

ui/display/screen.cc

Index: ui/display/screen.cc
diff --git a/ui/display/screen.cc b/ui/display/screen.cc
index 25f688219985aca631b5837818acaf34955a5a95..020a81781f9aeea06ea5ab261cf9e79ec04b0e5b 100644
--- a/ui/display/screen.cc
+++ b/ui/display/screen.cc
@@ -46,4 +46,10 @@ gfx::Rect Screen::DIPToScreenRectInWindow(gfx::NativeView view,
   return ScaleToEnclosingRect(dip_rect, scale);
 }
 
+float Screen::GetScaleFactorForWindow(gfx::NativeView view) const {
+  const display::Display& nearest_display = GetDisplayNearestWindow(view);
+  DCHECK(nearest_display.is_valid());
+  return nearest_display.device_scale_factor();
+}
+
 }  // namespace display