remove support for serialized pictures before aug 2019

Change-Id: I9b2a2dbac4110665e06882b9cbbc6f59e6bc0c21
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/302397
Reviewed-by: Ben Wagner <bungeman@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Reed <reed@google.com>
17 files changed