Use override in more classes in fpdfsdk/

fpdfsdk/src/fsdk_rendercontext.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 "../include/fsdk_rendercontext.h"
 
 void CRenderContext::Clear() {
   m_pDevice = NULL;
@@ skipping 18 matching lines @@
   delete m_pBitmap;
   if (m_hBitmap)
     DeleteObject(m_hBitmap);
 #endif
 }
 
 IFSDK_PAUSE_Adapter::IFSDK_PAUSE_Adapter(IFSDK_PAUSE* IPause) {
   m_IPause = IPause;
 }
 
+IFSDK_PAUSE_Adapter::~IFSDK_PAUSE_Adapter() {
+}
+
 FX_BOOL IFSDK_PAUSE_Adapter::NeedToPauseNow() {
   if (m_IPause->NeedToPauseNow) {
     return m_IPause->NeedToPauseNow(m_IPause);
   }
   return FALSE;
 }