Convert FWL_ERR into an enum class.

xfa/fwl/core/fwl_timerimp.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "xfa/fwl/core/fwl_appimp.h"
 #include "xfa/fwl/core/ifwl_adapternative.h"
 #include "xfa/fwl/core/ifwl_app.h"
 #include "xfa/fwl/core/ifwl_timer.h"
 #include "xfa/fwl/core/include/ifwl_adaptertimermgr.h"
 
 FWL_HTIMER FWL_StartTimer(IFWL_Timer* pTimer,
                           uint32_t dwElapse,
                           FX_BOOL bImmediately) {
   IFWL_AdapterNative* pAdapterNative = FWL_GetAdapterNative();
   if (!pAdapterNative)
     return NULL;
   IFWL_AdapterTimerMgr* pAdapterTimerMgr = pAdapterNative->GetTimerMgr();
   if (!pAdapterTimerMgr)
     return NULL;
   FWL_HTIMER hTimer = NULL;
   pAdapterTimerMgr->Start(pTimer, dwElapse, hTimer, bImmediately);
   return hTimer;
 }
-int32_t FWL_StopTimer(FWL_HTIMER hTimer) {
+
+FWL_Error FWL_StopTimer(FWL_HTIMER hTimer) {
   IFWL_AdapterNative* 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);
 }