Move xfa/fwl/core to xfa/fwl.

xfa/fwl/core/cfwl_msgmousewheel.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_msgmousewheel.h"
-
-#include <memory>
-
-#include "third_party/base/ptr_util.h"
-
-CFWL_MsgMouseWheel::CFWL_MsgMouseWheel(CFWL_Widget* pSrcTarget,
-                                       CFWL_Widget* pDstTarget)
-    : CFWL_Message(CFWL_Message::Type::MouseWheel, pSrcTarget, pDstTarget) {}
-
-CFWL_MsgMouseWheel::~CFWL_MsgMouseWheel() {}
-
-std::unique_ptr<CFWL_Message> CFWL_MsgMouseWheel::Clone() {
-  return pdfium::MakeUnique<CFWL_MsgMouseWheel>(*this);
-}