- Unify DepthStencilState and BlendState caches in RenderStateCache with those in Clear11. This
will increase cache hit rate and reduce memory usage.
- Apply DepthStencilState and BlendState only when required to reduce state sets.

BUG=angleproject:1632

Change-Id: I244e3ba189f82814638fa90e2617aa5441024d0f
Reviewed-on: https://chromium-review.googlesource.com/453888
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>