NS_IF_RELEASE(mStyleContext); if (nsnull != aContext) { mStyleContext = aContext; NS_ADDREF(aContext);
if (mStyleContext) mStyleContext->Release(); mStyleContext = aContext; if (aContext) { aContext->AddRef();
  nsresult SetStyleContext(nsIPresContext*  aPresContext, nsIStyleContext* aContext) {     if (aContext != mStyleContext) {      NS_IF_RELEASE(mStyleContext);      if (nsnull != aContext) {        mStyleContext = aContext;        NS_ADDREF(aContext);        DidSetStyleContext(aPresContext);      }    }    return NS_OK;  }