Two silly mistakes were landed in 9aded1:
 * The cache was not updating the sampler state it was using to compare
   against new ones.
 * The SamplerCompletenessCache entry was being copied and not updated.

BUG=709980

Change-Id: I1914ed30e24b9e48c4504da164f013a637a0b6c2
Reviewed-on: https://chromium-review.googlesource.com/475752Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>