Rename IFWL classes which do not have CFWL equivalents

xfa/fwl/core/ifwl_comboboxproxy.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_COMBOBOXPROXY_H_
-#define XFA_FWL_CORE_IFWL_COMBOBOXPROXY_H_
-
-#include <memory>
-
-#include "xfa/fwl/core/ifwl_formproxy.h"
-
-class IFWL_ComboBox;
-
-class IFWL_ComboBoxProxy : public IFWL_FormProxy {
- public:
-  IFWL_ComboBoxProxy(IFWL_ComboBox* pCombobBox,
-                     const CFWL_App* app,
-                     std::unique_ptr<CFWL_WidgetProperties> properties,
-                     IFWL_Widget* pOuter);
-  ~IFWL_ComboBoxProxy() override;
-
-  // IFWL_FormProxy
-  void OnProcessMessage(CFWL_Message* pMessage) override;
-  void OnDrawWidget(CFX_Graphics* pGraphics,
-                    const CFX_Matrix* pMatrix) override;
-
-  void Reset() { m_bLButtonUpSelf = false; }
-
- private:
-  void OnLButtonDown(CFWL_Message* pMsg);
-  void OnLButtonUp(CFWL_Message* pMsg);
-  void OnFocusChanged(CFWL_Message* pMsg, bool bSet);
-
-  bool m_bLButtonDown;
-  bool m_bLButtonUpSelf;
-  IFWL_ComboBox* m_pComboBox;
-};
-
-#endif  // XFA_FWL_CORE_IFWL_COMBOBOXPROXY_H_