Well - frankly I price this at "free-fiddy" because I hammered this out in 5m (just drop it into your console):
https://kopy.io/sAgzt
Yes it's jQuery (and I know everyone on HN hates jQuery!) - a vanilla JS version would be just as trivial! Wrapping it in a Chrome manifest w/a simple "enable/disable" browser button-type interface would be about 20 minutes I guess.