Convert FWL_ERR into an enum class.

fpdfsdk/fpdfxfa/include/fpdfxfa_util.h

 // 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
 
 #ifndef FPDFSDK_FPDFXFA_INCLUDE_FPDFXFA_UTIL_H_
 #define FPDFSDK_FPDFXFA_INCLUDE_FPDFXFA_UTIL_H_
 
 #include <vector>
 
 #include "fpdfsdk/fpdfxfa/include/fpdfxfa_doc.h"
 #include "xfa/fwl/core/include/ifwl_adaptertimermgr.h"
 
 #define JS_STR_VIEWERTYPE_STANDARD L"Exchange"
 #define JS_STR_LANGUANGE L"ENU"
 #define JS_STR_VIEWERVARIATION L"Full"
 #define JS_STR_VIEWERVERSION_XFA L"11"
 
 struct CFWL_TimerInfo;
 
 class CXFA_FWLAdapterTimerMgr : public IFWL_AdapterTimerMgr {
  public:
   CXFA_FWLAdapterTimerMgr(CPDFDoc_Environment* pEnv) : m_pEnv(pEnv) {}
-  virtual FWL_ERR Start(IFWL_Timer* pTimer,
-                        uint32_t dwElapse,
-                        FWL_HTIMER& hTimer,
-                        FX_BOOL bImmediately = TRUE);
-  virtual FWL_ERR Stop(FWL_HTIMER hTimer);
+  virtual FWL_Error Start(IFWL_Timer* pTimer,
+                          uint32_t dwElapse,
+                          FWL_HTIMER& hTimer,
+                          FX_BOOL bImmediately = TRUE);
+  virtual FWL_Error Stop(FWL_HTIMER hTimer);
 
  protected:
   static void TimerProc(int32_t idEvent);
 
   static std::vector<CFWL_TimerInfo*>* s_TimerArray;
   CPDFDoc_Environment* const m_pEnv;
 };
 
 struct CFWL_TimerInfo {
   CFWL_TimerInfo() : pTimer(nullptr) {}
   CFWL_TimerInfo(int32_t event, IFWL_Timer* timer)
       : idEvent(event), pTimer(timer) {}
 
   int32_t idEvent;
   IFWL_Timer* pTimer;
 };
 
 #endif  // FPDFSDK_FPDFXFA_INCLUDE_FPDFXFA_UTIL_H_