There are two main optimizations:

1. Inline setDraw*State and maskOutInactiveOutputDrawBuffers.
2. Remove Multiview dirty bits.

The first change is a refactoring only. It moves the code around a bit
so we can hit a fast path and never have to push/pop registers. The
second change is also a no-op since the multiview dirty bits were made
redundant.

Improves performance in the command buffer perftests by 1-5%.

Bug: angleproject:2877
Change-Id: I1632a838371ec8b85c2e06b3b86f08727ca9dacf
Reviewed-on: https://chromium-review.googlesource.com/c/1293629
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>