Split the common event classes out to files.

xfa/fwl/core/ifwl_widget.cpp

 // Copyright 2014 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/ifwl_widget.h"
 
 #include <algorithm>
 
 #include "xfa/fde/tto/fde_textout.h"
+#include "xfa/fwl/core/cfwl_evtkey.h"
+#include "xfa/fwl/core/cfwl_evtkillfocus.h"
+#include "xfa/fwl/core/cfwl_evtmouse.h"
+#include "xfa/fwl/core/cfwl_evtmousewheel.h"
+#include "xfa/fwl/core/cfwl_evtsetfocus.h"
+#include "xfa/fwl/core/cfwl_evtsizechanged.h"
 #include "xfa/fwl/core/cfwl_msgkey.h"
 #include "xfa/fwl/core/cfwl_msgkillfocus.h"
 #include "xfa/fwl/core/cfwl_msgmouse.h"
 #include "xfa/fwl/core/cfwl_msgmousewheel.h"
 #include "xfa/fwl/core/cfwl_msgsetfocus.h"
 #include "xfa/fwl/core/cfwl_themebackground.h"
 #include "xfa/fwl/core/cfwl_themepart.h"
 #include "xfa/fwl/core/cfwl_themetext.h"
 #include "xfa/fwl/core/cfwl_widgetmgr.h"
 #include "xfa/fwl/core/fwl_noteimp.h"
@@ skipping 720 matching lines @@
     }
     default:
       break;
   }
 }
 
 void IFWL_Widget::OnProcessEvent(CFWL_Event* pEvent) {}
 
 void IFWL_Widget::OnDrawWidget(CFX_Graphics* pGraphics,
                                const CFX_Matrix* pMatrix) {}