Refactor StateManager11 for dirty bits. This will make iterating over an internal set of dirty bits simpler. This also reorganizes the framebuffer invalidation logic a bit, including how the sample count is pulled from the Framebuffer. BUG=angleproject:1156 Change-Id: I79dbcd11704ab52568c587d836af9c1bff1d2d1f Reviewed-on: https://chromium-review.googlesource.com/529708 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>