Convert FWL_ERR into an enum class.

xfa/fwl/core/fwl_timerimp.cpp

Index: xfa/fwl/core/fwl_timerimp.cpp
diff --git a/xfa/fwl/core/fwl_timerimp.cpp b/xfa/fwl/core/fwl_timerimp.cpp
index 5adf8e158c1e689bbd2757f7d9cd09180f6c1c1c..ced5adeb9df8e33aa3ea7d593f3c5cf4f3459498 100644
--- a/xfa/fwl/core/fwl_timerimp.cpp
+++ b/xfa/fwl/core/fwl_timerimp.cpp
@@ -23,12 +23,14 @@ FWL_HTIMER FWL_StartTimer(IFWL_Timer* pTimer,
   pAdapterTimerMgr->Start(pTimer, dwElapse, hTimer, bImmediately);
   return hTimer;
 }
-int32_t FWL_StopTimer(FWL_HTIMER hTimer) {
+
+FWL_Error FWL_StopTimer(FWL_HTIMER hTimer) {
   CXFA_FFApp* pAdapterNative = FWL_GetAdapterNative();
   if (!pAdapterNative)
-    return FWL_ERR_Indefinite;
+    return FWL_Error::Indefinite;
+
   IFWL_AdapterTimerMgr* pAdapterTimerMgr = pAdapterNative->GetTimerMgr();
   if (!pAdapterTimerMgr)
-    return FWL_ERR_Indefinite;
+    return FWL_Error::Indefinite;
   return pAdapterTimerMgr->Stop(hTimer);
 }