Convert FWL_ERR into an enum class.

xfa/fxfa/app/xfa_ffcheckbutton.cpp

Index: xfa/fxfa/app/xfa_ffcheckbutton.cpp
diff --git a/xfa/fxfa/app/xfa_ffcheckbutton.cpp b/xfa/fxfa/app/xfa_ffcheckbutton.cpp
index b75fcd5ab08d5468efbbeb8986750b16f35bc1b1..953cd7c493eb1a8af1c82da9244c7efb93e1121c 100644
--- a/xfa/fxfa/app/xfa_ffcheckbutton.cpp
+++ b/xfa/fxfa/app/xfa_ffcheckbutton.cpp
@@ -299,7 +299,7 @@ int32_t CXFA_FFCheckButton::OnProcessMessage(CFWL_Message* pMessage) {
   return m_pOldDelegate->OnProcessMessage(pMessage);
 }
 
-FWL_ERR CXFA_FFCheckButton::OnProcessEvent(CFWL_Event* pEvent) {
+FWL_Error CXFA_FFCheckButton::OnProcessEvent(CFWL_Event* pEvent) {
   CXFA_FFField::OnProcessEvent(pEvent);
   switch (pEvent->GetClassID()) {
     case CFWL_EventType::CheckStateChanged: {
@@ -333,7 +333,7 @@ FWL_ERR CXFA_FFCheckButton::OnProcessEvent(CFWL_Event* pEvent) {
   return m_pOldDelegate->OnProcessEvent(pEvent);
 }
 
-FWL_ERR CXFA_FFCheckButton::OnDrawWidget(CFX_Graphics* pGraphics,
-                                         const CFX_Matrix* pMatrix) {
+FWL_Error CXFA_FFCheckButton::OnDrawWidget(CFX_Graphics* pGraphics,
+                                           const CFX_Matrix* pMatrix) {
   return m_pOldDelegate->OnDrawWidget(pGraphics, pMatrix);
 }