Mac GL drivers generat errors when binding transform feedback buffers
with glBindBufferBase/glBindBufferRange when the buffer has not been
bound to any binding point before. Work around this by simply binding
the buffer first.

Bug: angleproject:5140
Change-Id: I1895f8367412135c100a5072117c929be8a8e90b
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2461826
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>