mRefCnt = 0;
PresShell::~PresShell(){  if (nsnull != mDocument) {    mDocument->DeleteShell(this);    NS_RELEASE(mDocument);  }  if (nsnull != mRootFrame) {    mRootFrame->DeleteFrame();  }  NS_IF_RELEASE(mPresContext);  NS_IF_RELEASE(mViewManager);  NS_IF_RELEASE(mStyleSet);}