Only dirty the uniforms if the uniforms are dirty. This gives about a
20% reduction in ANGLE overhead on a targeted micro-benchmark. It
probably won't have that large of an impact on most real-world
applications, but it was strictly unnecessary work.

Something that came up when investigating the internal program binary
cache in ANGLE D3D11.

BUG=angleproject:2053

Change-Id: I2d55c010c29ce9627a9001dd2abe6e549f0b7e8c
Reviewed-on: https://chromium-review.googlesource.com/524297Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>