In case it helps--calling window.scrollTo(window.scrollX, window.scrollY) right after I hit the back button appears to get my browser out of the broken state from the second repro (first one no longer works for me). Might it work to call that at various points when Chrome might have entered a broken state?

Yep, the repro works for me. Sorry for blaming Phab! I guess it's just the only site I noticed it on since I use it so often.

Holy cow, that's some dedication. Thanks, guys!

@chad: Good call. I've been using trackpad/2-finger scrolling. Does not repro for me with keyboard scrolling, so may not work with mousewheel either.

Hmm, just found an alternate repro that may work better?