mParser(nsnull),
XULDocumentImpl::XULDocumentImpl(void)    : mArena(nsnull),      mDocumentURL(nsnull),      mDocumentURLGroup(nsnull),      mRootContent(nsnull),      mParentDocument(nsnull),      mScriptContextOwner(nsnull),      mScriptObject(nsnull),      mSelection(nsnull),      mDisplaySelection(PR_FALSE),      mNameSpaceManager(nsnull),      mAttrStyleSheet(nsnull),      mRDFService(nsnull),      mBuilders(nsnull),      mXULBuilder(nsnull),      mLocalDataSource(nsnull),      mDocumentDataSource(nsnull),      mParser(nsnull),      mLineBreaker(nsnull),      mWordBreaker(nsnull),      mContentViewerContainer(nsnull),      mCommand(""),      mFragmentRoot(nsnull){    NS_INIT_REFCNT();    nsresult rv;    // construct a selection object    if (NS_FAILED(rv = nsComponentManager::CreateInstance(kRangeListCID,                                                    nsnull,                                                    kIDOMSelectionIID,                                                    (void**) &mSelection))) {        NS_ERROR("unable to create DOM selection");    }    if (gRefCnt++ == 0) {        kIdAtom        = NS_NewAtom("id");        kObservesAtom  = NS_NewAtom("observes");    }#ifdef PR_LOGGING    if (! gMapLog)        gMapLog = PR_NewLogModule("nsXULDocumentElementMap");#endif}