runtime registration for decoders

What do you think of this sort of thing for letting
users register codecs at runtime instead of at build time?

Change-Id: I448ea3466862326c283ad9b2f1b7eea56cffc80c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/210449
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
3 files changed