missingFamilyList->Append(NS_LITERAL_STRING(", "));
missingFamilyList->AppendLiteral(", ");
MathFontEnumCallback(const nsString& aFamily, PRBool aGeneric, void *aData){  // check if the font is missing  MathFontEnumContext* context = (MathFontEnumContext*)aData;  nsIPresContext* presContext = context->mPresContext;  nsString* missingFamilyList = context->mMissingFamilyList;  if (!CheckFontExistence(presContext, aFamily)) {//#ifndef _WIN32   // XXX In principle, the mathfont-family list in the mathfont.properties file   // is customizable depending on the platform. For now, this is here since there   // is no need to alert Linux users about TrueType fonts specific to Windows.   if (aFamily.EqualsIgnoreCase("MT Extra"))     return PR_TRUE; // continue to try other fonts//#endif    if (!missingFamilyList->IsEmpty()) {      missingFamilyList->Append(NS_LITERAL_STRING(", "));    }    missingFamilyList->Append(aFamily);  }  if (!gGlyphTableList->AddGlyphTable(aFamily))    return PR_FALSE; // stop in low-memory situations  return PR_TRUE; // don't stop}