Make addTexture/BufferAccess on GrProcessor non-virtual

Perhaps these needed to be virtual in the past, but no longer.

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4120

Change-Id: I1ba713a1da713f2c7955c0cfc9931917f2719a63
Reviewed-on: https://skia-review.googlesource.com/4120
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
3 files changed