Fix -Wnon-virtual-dtor compiler warnings.

fpdfsdk/include/pdfwindow/PWL_EditCtrl.h

 // 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
 
 #ifndef _PWL_EDITCTRL_H_
 #define _PWL_EDITCTRL_H_
 
 enum PWL_EDIT_ALIGNFORMAT_H
@@ skipping 12 matching lines @@
 
 class IPWL_Edit_Notify;
 class CPWL_EditCtrl;
 class CPWL_Caret;
 class IFX_Edit;
 class CPWL_Edit;
 
 class IPWL_Edit_Notify
 {
 public:
+        virtual ~IPWL_Edit_Notify() { }
         //when the position of caret is changed in edit
         virtual void                                    OnCaretMove(FX_INT32 x1, FX_INT32 y1, FX_INT32 x2, FX_INT32 y2) {}
         virtual void                                    OnContentChange(const CPDF_Rect& rcContent){}
         //OprType: 0 InsertWord
         //1 InsertReturn
         //2 BackSpace
         //3 Delete
         //4 Clear
         //5 InsertText
         //6 SetText
@@ skipping 119 matching lines @@
         FX_BOOL                                                 m_bMouseDown;
         IPWL_Edit_Notify*                               m_pEditNotify;  
 
 private:
         FX_INT32                                                m_nCharSet;
         FX_INT32                                                m_nCodePage;
 };
 
 #endif