Move xfa/fwl/core to xfa/fwl.

xfa/fwl/core/cfwl_eventtarget.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_EVENTTARGET_H_
-#define XFA_FWL_CORE_CFWL_EVENTTARGET_H_
-
-#include <set>
-
-#include "core/fxcrt/fx_basic.h"
-#include "xfa/fwl/core/cfwl_event.h"
-
-class CFWL_Event;
-class CFWL_Widget;
-
-class CFWL_EventTarget {
- public:
-  explicit CFWL_EventTarget(CFWL_Widget* pListener);
-  ~CFWL_EventTarget();
-
-  void SetEventSource(CFWL_Widget* pSource);
-  bool ProcessEvent(CFWL_Event* pEvent);
-
-  bool IsInvalid() const { return m_bInvalid; }
-  void FlagInvalid() { m_bInvalid = true; }
-
- private:
-  std::set<CFWL_Widget*> m_widgets;
-  CFWL_Widget* m_pListener;
-  bool m_bInvalid;
-};
-
-#endif  // XFA_FWL_CORE_CFWL_EVENTTARGET_H_