mViewManager->EnableRefresh();
mViewManager->EnableRefresh(NS_VMREFRESH_IMMEDIATE);
DocumentViewerImpl::SetEnableRendering(PRBool aOn){  mEnableRendering = aOn;  if (mViewManager) {    if (aOn) {      mViewManager->EnableRefresh();      nsIView* view;       mViewManager->GetRootView(view);   // views are not refCounted       if (view) {         mViewManager->UpdateView(view, NS_VMREFRESH_IMMEDIATE);      }     }    else {      mViewManager->DisableRefresh();    }  }  return NS_OK;}