Convert FWL_ERR into an enum class.

xfa/fwl/theme/cfwl_pushbuttontp.cpp

Index: xfa/fwl/theme/cfwl_pushbuttontp.cpp
diff --git a/xfa/fwl/theme/cfwl_pushbuttontp.cpp b/xfa/fwl/theme/cfwl_pushbuttontp.cpp
index 780c5803695dd0ccd1c739689e1d6e68f0f27f6a..103bae7aa9f9053d71444c0a916120c96dce9c70 100644
--- a/xfa/fwl/theme/cfwl_pushbuttontp.cpp
+++ b/xfa/fwl/theme/cfwl_pushbuttontp.cpp
@@ -102,11 +102,11 @@ void* CFWL_PushButtonTP::GetCapacity(CFWL_ThemePart* pThemePart,
   }
   return CFWL_WidgetTP::GetCapacity(pThemePart, dwCapacity);
 }
-FWL_ERR CFWL_PushButtonTP::Initialize() {
+FWL_Error CFWL_PushButtonTP::Initialize() {
   InitTTO();
   return CFWL_WidgetTP::Initialize();
 }
-FWL_ERR CFWL_PushButtonTP::Finalize() {
+FWL_Error CFWL_PushButtonTP::Finalize() {
   FinalizeTTO();
   return CFWL_WidgetTP::Finalize();
 }