fix serializing shadowrec

follow-up to https://skia-review.googlesource.com/95741

Interestingly, due to 7530, this CL will not actually get exercised by the bots.

Bug: skia:7530
Change-Id: I93043e82ee672d4b425b79360e3d03346afad7fe
Reviewed-on: https://skia-review.googlesource.com/99323
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed