if (!clone) {
if (!clone || !clone->mDeclaration || (!clone->mSelector != !mSelector)) { delete clone;
CSSStyleRuleImpl::Clone(nsICSSRule*& aClone) const{  CSSStyleRuleImpl* clone = new CSSStyleRuleImpl(*this);  if (!clone) {    aClone = nsnull;    return NS_ERROR_OUT_OF_MEMORY;  }  return CallQueryInterface(clone, &aClone);}