Convert single use EventTypes to class files.

xfa/fwl/core/cfwl_evtcheckstatechanged.h

 // Copyright 2016 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_CFWL_EVTKEY_H_
-#define XFA_FWL_CORE_CFWL_EVTKEY_H_
+#ifndef XFA_FWL_CORE_CFWL_EVTCHECKSTATECHANGED_H_
+#define XFA_FWL_CORE_CFWL_EVTCHECKSTATECHANGED_H_
 
 #include "xfa/fwl/core/cfwl_event.h"
 
-class CFWL_EvtKey : public CFWL_Event {
+class CFWL_EvtCheckStateChanged : public CFWL_Event {
  public:
-  CFWL_EvtKey();
-  ~CFWL_EvtKey() override;
+  CFWL_EvtCheckStateChanged();
+  ~CFWL_EvtCheckStateChanged() override;
 
   CFWL_EventType GetClassID() const override;
-
-  uint32_t m_dwKeyCode;
-  uint32_t m_dwFlags;
-  FWL_KeyCommand m_dwCmd;
 };
 
-#endif  // XFA_FWL_CORE_CFWL_EVTKEY_H_
+#endif  // XFA_FWL_CORE_CFWL_EVTCHECKSTATECHANGED_H_