Support serialization of child effects for Runtime Blenders.

This CL also factors out the child effect reading and writing code into
helper functions, to avoid repeating it verbatim.

Change-Id: Ia48e5f346aa557179bec83daaa91e772765181a1
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/434117
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
1 file changed