Make a context current when destroying it. The destructors of objects in a context assume that the context is current during destruction. If another context is current at this time, they can delete objects from other contexts. BUG=angleproject:2464 Change-Id: I813d092cc7f33a39c814edae5baa433733b4590c Reviewed-on: https://chromium-review.googlesource.com/1083371 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Yuly Novikov <ynovikov@chromium.org>