Remove FWL_WGTHITTEST_* defines in favour of enum class.

xfa/fwl/lightwidget/cfwl_widget.cpp

Index: xfa/fwl/lightwidget/cfwl_widget.cpp
diff --git a/xfa/fwl/lightwidget/cfwl_widget.cpp b/xfa/fwl/lightwidget/cfwl_widget.cpp
index 98a5a22f4398c91ba1937a17d8547ea052d783ea..ff28b376469a8dc7fdfee72a1424efca7b25b1cb 100644
--- a/xfa/fwl/lightwidget/cfwl_widget.cpp
+++ b/xfa/fwl/lightwidget/cfwl_widget.cpp
@@ -164,9 +164,9 @@ FWL_ERR CFWL_Widget::UnlockUpdate() {
   return m_pIface->UnlockUpdate();
 }
 
-uint32_t CFWL_Widget::HitTest(FX_FLOAT fx, FX_FLOAT fy) {
+FWL_WidgetHit CFWL_Widget::HitTest(FX_FLOAT fx, FX_FLOAT fy) {
   if (!m_pIface)
-    return 0;
+    return FWL_WidgetHit::Unknown;
   return m_pIface->HitTest(fx, fy);
 }