Remove unused processor custom feature tracking

Change-Id: Iba3db4545360c0854076ad914358cd645737aa04
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/438736
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
8 files changed