code: function filterRulesByElementAndProp(rules, element, prop) {
  	var foundRules = [];
  	if (element.id) {
  		foundRules = foundRules.concat(rules['#' + element.id] || []);
  	}
  	(element.getAttribute('class') || '').split(/\s+/).forEach(function(className) {
  		foundRules = foundRules.concat(rules['.' + className] || []);
  	});
  	foundRules = foundRules
  		.concat(rules[element.tagName.toLowerCase()] || [])
  		.concat(rules['*'] || []);
  	return foundRules.filter(function(rule) {
  		return rule._rule.style.getPropertyValue(prop)
  			&& (
  				!rule._rule.parentRule
  				|| rule._rule.parentRule.type !== 4 // @media rule
  				|| matchesMedia(rule._rule.parentRule.media.mediaText)
  			)
  			&& elementMatchesSelector(element, rule._selector);
  	});
  }
docs: Filter rules by matching the element and at least one property
  
  @param  {{<string>: Array.<{_selector: string, _rule: CSSRule}>}} rules
  @param  {Element}                                                 element
  @param  {string}                                                  prop
  @return {Array.<{_selector: string, _rule: CSSRule}>}