NS_ASSERTION(mStackPos == 1, "insufficient close container calls");
SinkContext::End(){  NS_ASSERTION(mStackPos == 1, "insufficient close container calls");  for (PRInt32 i = 0; i < mStackPos; i++) {    NS_RELEASE(mStack[i].mContent);  }  mStackPos = 0;  mTextLength = 0;  return NS_OK;}