Move xfa/fwl/core to xfa/fwl.

xfa/fwl/core/cfwl_message.cpp

-// 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
-
-#include "xfa/fwl/core/cfwl_message.h"
-
-CFWL_Message::CFWL_Message(CFWL_Message::Type type)
-    : CFWL_Message(type, nullptr, nullptr) {}
-
-CFWL_Message::CFWL_Message(Type type, CFWL_Widget* pSrcTarget)
-    : CFWL_Message(type, pSrcTarget, nullptr) {}
-
-CFWL_Message::CFWL_Message(Type type,
-                           CFWL_Widget* pSrcTarget,
-                           CFWL_Widget* pDstTarget)
-    : m_pSrcTarget(pSrcTarget),
-      m_pDstTarget(pDstTarget),
-      m_type(type) {}
-
-CFWL_Message::~CFWL_Message() {}
-
-std::unique_ptr<CFWL_Message> CFWL_Message::Clone() {
-  return nullptr;
-}