We now have a new type of ProgramKind, private runtime shaders.
`sksl_rt_effect.sksl` is now only loaded for these kinds of program.
Rather than having a special-case check for sk_FragCoord in
SkRuntimeEffect, the symbol will no longer exist at all unless a private
options flag is set.
Change-Id: I9223baaf59d74c44d64f322cd57fc841625342b7
Bug: skia:12202
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/532784
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
c6b2e7115a