The transform feedback generic binding point is not part of the
transform feedback object and is not used for transform feedback. Only
the indexed binding points are used. A buffer that is bound to the
generic binding point should be usable for either transform feedback or
non-transform-feedback purposes.

Bug: 853978
Change-Id: I5b730212c65524188134ac34645328328664f0a4
Reviewed-on: https://chromium-review.googlesource.com/1112841
Commit-Queue: James Darpinian <jdarpinian@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>