Cleanup remaining IFWL files for visiblity and usage.

xfa/fwl/core/ifwl_adaptertimermgr.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 XFA_FWL_CORE_IFWL_ADAPTERTIMERMGR_H_
 #define XFA_FWL_CORE_IFWL_ADAPTERTIMERMGR_H_
 
-#include "xfa/fwl/core/fwl_error.h"
 #include "xfa/fwl/core/ifwl_timer.h"
 
 class IFWL_AdapterTimerMgr {
  public:
   virtual ~IFWL_AdapterTimerMgr() {}
-  virtual FWL_Error Start(IFWL_Timer* pTimer,
-                          uint32_t dwElapse,
-                          bool bImmediately,
-                          IFWL_TimerInfo** pTimerInfo) = 0;
-  virtual FWL_Error Stop(IFWL_TimerInfo* pTimerInfo) = 0;
+  virtual void Start(IFWL_Timer* pTimer,
+                     uint32_t dwElapse,
+                     bool bImmediately,
+                     IFWL_TimerInfo** pTimerInfo) = 0;
+  virtual void Stop(IFWL_TimerInfo* pTimerInfo) = 0;
 };
 
 #endif  // XFA_FWL_CORE_IFWL_ADAPTERTIMERMGR_H_