syncPrimitiveTopology checks the transform feedback state, so it needs
to be called whenever the transform feedback state changes. This fixes
flakes in the WebGL 2 conformance test
transform_feedback/simultaneous_binding.html

Bug: 696345
Change-Id: I4e17bbf60b4a387cc23dc55bd5a051f5da9fa66e
Reviewed-on: https://chromium-review.googlesource.com/1006489
Commit-Queue: James Darpinian <jdarpinian@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>