if (aHandleContainer && mSheet) {
if (aHandleContainer) { NS_ASSERTION(mSheet, "rule must be in a sheet");
CSSStyleRuleImpl::DeclarationChanged(PRBool aHandleContainer){  CSSStyleRuleImpl* clone = new CSSStyleRuleImpl(*this, mDeclaration);  if (!clone) {    return nsnull;  }  NS_ADDREF(clone); // for return  if (aHandleContainer && mSheet) {    if (mParentRule) {      mSheet->ReplaceRuleInGroup(mParentRule, this, clone);    } else {      mSheet->ReplaceStyleRule(this, clone);    }  }  return clone;}