upgrade SkReadBuffer to always validate

Bug: skia:
Change-Id: I054560b66c6cde346d939015326d8547879d2c4b
Reviewed-on: https://skia-review.googlesource.com/81160
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Reed <reed@google.com>
16 files changed