If glViewport() or glScissor() is called with same
info, skip updating viewport or scissor info and
related dirty bits.

Bug: angleproject:4487
Change-Id: I9a0f3eb0df789beb99447ebc98383f502fbc763d
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2105528
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>