Move xfa/fwl/core to xfa/fwl.

xfa/fwl/core/ifwl_widgetdelegate.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_IFWL_WIDGETDELEGATE_H_
-#define XFA_FWL_CORE_IFWL_WIDGETDELEGATE_H_
-
-#include <stdint.h>
-
-class CFWL_Event;
-class CFWL_Message;
-class CFX_Graphics;
-class CFX_Matrix;
-
-class IFWL_WidgetDelegate {
- public:
-  virtual ~IFWL_WidgetDelegate() {}
-
-  virtual void OnProcessMessage(CFWL_Message* pMessage) = 0;
-  virtual void OnProcessEvent(CFWL_Event* pEvent) = 0;
-  virtual void OnDrawWidget(CFX_Graphics* pGraphics,
-                            const CFX_Matrix* pMatrix) = 0;
-};
-
-#endif  // XFA_FWL_CORE_IFWL_WIDGETDELEGATE_H_