Split the common event classes out to files.

xfa/fxfa/app/xfa_fffield.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/fxfa/app/xfa_fffield.h"
 
 #include "xfa/fwl/core/cfwl_edit.h"
+#include "xfa/fwl/core/cfwl_evtmouse.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_picturebox.h"
 #include "xfa/fwl/core/cfwl_widgetmgr.h"
 #include "xfa/fwl/core/ifwl_edit.h"
 #include "xfa/fxfa/app/xfa_fwltheme.h"
 #include "xfa/fxfa/app/xfa_textlayout.h"
@@ skipping 794 matching lines @@
       m_pDataAcc->ProcessEvent(XFA_ATTRIBUTEENUM_Click, &eParam);
       break;
     }
     default:
       break;
   }
 }
 
 void CXFA_FFField::OnDrawWidget(CFX_Graphics* pGraphics,
                                 const CFX_Matrix* pMatrix) {}