Setting filename to view title token doesn't work if using contextual filter to override title

Setting a data export display filename to "[view:title].csv" and overriding the display title via a contextual filter doesn't work: the filename remains set to the non-overridden Title from the main View config area. Updating the filename via Views hooks doesn't work either.

This appears to be a regression issue as this wasn't an issue until beta2, when the way file names were set got changed. I will attach a patch shortly that reverts those changes, in case that helps anyone else.