Chrome Version       : 49.0.2623.112 (Official Build) (64-bit)
URLs (if applicable) : https://jsfiddle.net/asbjornh/sgnm0q7n/
Other browsers tested:
  Add OK or FAIL, along with the version, after other browsers where you
have tested this issue:
     Safari: FAIL (9.1)
    Firefox: OK (44.0.2)
         IE: FAIL (11.0.29)

What steps will reproduce the problem?
(1) Open https://jsfiddle.net/asbjornh/sgnm0q7n/ in Chrome
(2) Mouse over the black square for 1-2 seconds and then remove the mouse cursor, interrupting the transition

What is the expected result?
That the reverse animation that happens once the mouse cursor is removed from the element lasts for as long as the transition had been running at the time of interruption. So, if the transition is interrupted at 2s, I expect the reverse animation to last 2 seconds. (Link to W3C and CSS transition reversing below)

What happens instead?
The reverse animation lasts for the full duration specified in transition-duration, making it appear very slow if the original transition is interrupted early on.


Please provide any additional information below. Attach a screenshot if
possible.

W3C describes transition interruptions here: https://www.w3.org/TR/css3-transitions/#reversing