If you need X requests served for a full page-load (or whichever for the primary functionality of the page), you should be totaling those request times into a single entry for your histogram, otherwise you are calculating the distribution of something potentially useless (e.g. 50% of page_is_broken_without_it.js might actually be in p99 even if that file is 1% of your requests and the generic histogram might look deceptively good).