Convert FWL_ERR into an enum class.

xfa/fwl/theme/cfwl_monthcalendartp.cpp

Index: xfa/fwl/theme/cfwl_monthcalendartp.cpp
diff --git a/xfa/fwl/theme/cfwl_monthcalendartp.cpp b/xfa/fwl/theme/cfwl_monthcalendartp.cpp
index 8b10fb993c794cc097a36f7248faa88254cc400b..fac318f69db4ca3bda1532e1ecf64b2af0196f05 100644
--- a/xfa/fwl/theme/cfwl_monthcalendartp.cpp
+++ b/xfa/fwl/theme/cfwl_monthcalendartp.cpp
@@ -349,11 +349,11 @@ void* CFWL_MonthCalendarTP::GetCapacity(CFWL_ThemePart* pThemePart,
   }
   return CFWL_WidgetTP::GetCapacity(pThemePart, dwCapacity);
 }
-FWL_ERR CFWL_MonthCalendarTP::Initialize() {
+FWL_Error CFWL_MonthCalendarTP::Initialize() {
   InitTTO();
   return CFWL_WidgetTP::Initialize();
 }
-FWL_ERR CFWL_MonthCalendarTP::Finalize() {
+FWL_Error CFWL_MonthCalendarTP::Finalize() {
   FinalizeTTO();
   return CFWL_WidgetTP::Finalize();
 }