bgrins/ExpandingTextareas — comment on commit e62afa1b773e1868c14d6e46d6f28f8f10b96a23
File:  line 0
By bgrins:

Yeah, I hate when that happens. I used the Chrome Devtools to figure that out. Right Click -> Inspect Element. Scroll down the right panel on the sidebar all the way down to 'Metrics'. I did that with the textarea that had the scrollbar and the pre (it works even on hidden elements), and it made it a lot easier to find (since I could see they weren't quite the same height - but obviously very close).