tell gms when they are being run in viewer

Motivated here: https://skia-review.googlesource.com/c/skia/+/291696

Change-Id: I7388c20fafc27684d55c1493a96fc3b5ccd88bea
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/292314
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed