An in-render-pass clear now pauses transform feedback so it wouldn't
contribute to it.  Since it's not possible to resume the transform
feedback in the same render pass (as it needs a memory barrier for its
counter buffer), the render pass is broken after the clear.

Bug: angleproject:5426
Change-Id: I1eaf8c153d076bd912a4a08c65960c12f00341ef
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2573579
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Charlie Lao <cclao@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>