ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
To this:
ga.src = 'https://ssl.google-analytics.com/ga.js';
While the Google Analytics JS is loaded over HTTPS, the tracking information sent back to Google inherits HTTP/HTTPS from the website itself.
That means if you're on a HTTP site, it'll send back the results over HTTP. You'd need to actually hand roll your own GA JS to have it send back over HTTPS and then I'm not certain if that'll cause issues with records at Google's end.
And for the newer analytics.js: https://developers.google.com/analytics/devguides/collection...