Optimize browser rendering

Optimize browser rendering
Web Performance Best Practices
Using Page Speed

isServingFromCache
http://page-speed.googlecode.com/svn/trunk/src/js/activity/request-observer.js

/**
 * @param {nsIRequest} request the request to get the URL for.
 * @return {boolean} whether the response is being served from cache.
 * @private
 */
activity.RequestObserver.isServingFromCache_ = function(request) {
  var cachingChannel =
      activity.xpcom.QI(request, activity.xpcom.CI('nsICachingChannel'));
  return request.isPending() && cachingChannel.isFromCache();
};

http://page-speed.googlecode.com/svn/trunk/src/js/closure/base.js

goog.inherits = function(childCtor, parentCtor) {
  /** @constructor */
  function tempCtor() {};
  tempCtor.prototype = parentCtor.prototype;
  childCtor.superClass_ = parentCtor.prototype;
  childCtor.prototype = new tempCtor();
  childCtor.prototype.constructor = childCtor;
};