test both JIT and interpreter

Add Program::dropJIT() to allow us to proactively drop
any JIT code forcing fallback on the interpreter,
and use it to test both on JIT-supported platforms.

Other platforms will just test the interpreter twice.

Change-Id: I607d00ef3c648e66a0b3a1374b11aa82dbfff70c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/227424
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Herb Derby <herb@google.com>
3 files changed