Requested by Flutter. This adds about 80k of code size
due in large part to the brotli decoding logic.
This also updates the check_deps error to point at
a doc on how to create a new GOB mirror.
Brotli version is 1.0.9; the latest as of today.
Change-Id: I1580cb2189ff1205a9bffca3d887ff2b98a4042e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/333218
Reviewed-by: Ben Wagner <bungeman@google.com>
Reviewed-by: Eric Boren <borenet@google.com>
Commit-Queue: Kevin Lubick <kjlubick@google.com>
