move all registration into optional hooks

I don't think there's any reason to register any of these types
for deserialization unless the client is using deserialization.

Change-Id: Iea02670f3b6e99851061ac4ec784a6f372a5903b
Reviewed-on: https://skia-review.googlesource.com/c/163988
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
4 files changed