Reduce RenderStateCache cache sizes from 4k to 2k. Saves 64kb of memory.

Change-Id: I9e92bbdf095f1e66cf9b84ba81899a8af59d6d86
Reviewed-on: https://chromium-review.googlesource.com/453886Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>