In Vector the language button is a checkbox. It uses the checkbox
hack to provide non-JS dropdown behaviour.
When the JS upgrades such a button, the checkbox behavior continues
to work. An unsatisfying hack in Vector workarounds this problem.
This provides a neater way to disable that behavior
in Vector once the button is clicked by adding support for the
well documented checkbox hack.
Bug: T283757
Change-Id: I97a69c30b27cb1ded06451389e086229561c3589
869c721e91