This will allow us to react to state change notifications for validation
caching. It also cleans up some of the logic in the D3D11 State Manager.

Bug: angleproject:2747
Change-Id: I85ed6404206c2b9bf504d552cf5751be56e62146
Reviewed-on: https://chromium-review.googlesource.com/1172086Reviewed-by: Frank Henigman <fjhenigman@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>