Add full compliment of operator*, have them assert in debug,
but not throw in release as per c++ spec.
Add full compliment of value() have them crash if there is
no value as per the c++ spec.
Add value_or.
Add test for value_or.
Change-Id: Ib0d9a01fba367768e66d00fbc61b471397e8582c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/425476
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
d390c642ac