Unify CFWL_WidgetProperties and CFWL_WidgetImpProperties.

xfa/fwl/core/cfwl_listbox.cpp

Index: xfa/fwl/core/cfwl_listbox.cpp
diff --git a/xfa/fwl/core/cfwl_listbox.cpp b/xfa/fwl/core/cfwl_listbox.cpp
index f7e167125de26602a95bc72227f43ab6a25231c9..859054005f889658ae21309f61bb5cd8444b89f4 100644
--- a/xfa/fwl/core/cfwl_listbox.cpp
+++ b/xfa/fwl/core/cfwl_listbox.cpp
@@ -27,7 +27,7 @@ void CFWL_ListBox::Initialize() {
   ASSERT(!m_pIface);
 
   m_pIface = pdfium::MakeUnique<IFWL_ListBox>(
-      m_pApp, m_pProperties->MakeWidgetImpProperties(&m_ListBoxDP), nullptr);
+      m_pApp, pdfium::MakeUnique<CFWL_WidgetProperties>(&m_ListBoxDP), nullptr);
 
   CFWL_Widget::Initialize();
 }