NS_PRECONDITION(!aData->mContent || aData->mContent->IsContentOfType(nsIContent::eELEMENT), "content (if present) must be element");
NS_PRECONDITION(aData->mContent->IsContentOfType(nsIContent::eELEMENT), "content must be element");
CSSRuleProcessor::RulesMatching(PseudoRuleProcessorData* aData,                                nsIAtom* aMedium){  NS_PRECONDITION(!aData->mContent ||                  aData->mContent->IsContentOfType(nsIContent::eELEMENT),                  "content (if present) must be element");  RuleCascadeData* cascade = GetRuleCascade(aData->mPresContext, aMedium);  if (cascade) {    cascade->mRuleHash.EnumerateTagRules(aData->mPseudoTag,                                         PseudoEnumFunc, aData);  }  return NS_OK;}