Cleanup unneeded FWL theme code.

xfa/fwl/core/fwl_widgetimp.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/fwl_widgetimp.h"
 
 #include <algorithm>
 
@@ skipping 620 matching lines @@
   if (m_pProperties->m_pThemeProvider) {
     return m_pProperties->m_pThemeProvider;
   }
   IFWL_Widget* pUp = m_pInterface;
   do {
     pUp = (pUp->GetStyles() & FWL_WGTSTYLE_Popup)
               ? m_pWidgetMgr->GetOwnerWidget(pUp)
               : m_pWidgetMgr->GetParentWidget(pUp);
     if (pUp) {
       IFWL_ThemeProvider* pRet = pUp->GetThemeProvider();
-      if (pRet && pRet->IsValidWidget(m_pInterface))
+      if (pRet)
         return pRet;
     }
   } while (pUp);
   return FWL_GetApp()->GetThemeProvider();
 }
 CFWL_WidgetImp* CFWL_WidgetImp::GetRootOuter() {
   IFWL_Widget* pRet = m_pOuter;
   if (!pRet)
     return nullptr;
   while (IFWL_Widget* pOuter = pRet->GetOuter()) {
@@ skipping 388 matching lines @@
   }
 }
 
 void CFWL_WidgetImpDelegate::OnProcessEvent(CFWL_Event* pEvent) {}
 
 void CFWL_WidgetImpDelegate::OnDrawWidget(CFX_Graphics* pGraphics,
                                           const CFX_Matrix* pMatrix) {
   CFWL_EvtDraw evt;
   evt.m_pGraphics = pGraphics;
 }