nsDocHeaderData(nsIAtom* aField, const nsString& aData)
nsDocHeaderData(nsIAtom* aField, const nsAReadableString& aData)
  nsDocHeaderData(nsIAtom* aField, const nsString& aData)  {    mField = aField;    NS_IF_ADDREF(mField);    mData.Assign(aData);    mNext = nsnull;  }