Dropped frames in dock slide out animation when the dock is hidden

[dpavlic]

From time to time the animation to bring the dock out when it is hidden stutters and lags (it appears to be dropping frames). This is on an admittedly very low end Toshiba 2 Chromebook Celeron, but I don't experience these issues with any stock GNOME 3 animations: it also doesn't happen all of the time with the extension either. Usually it happens over time I have GNOME 3 running and I can 'fix' it by restarting the GNOME session, but this is of course not ideal.

This affects me in the last dash-to-dock version and also the master. I have not checked if the issue occurs in the previous versions. The behaviour is also observed even if dash-to-dock is the only extension running.