add new gm for cmoposeshader

Bug: skia:
Change-Id: I8f0925743ea3a7f5bb2af31d01da7d932827d256
Reviewed-on: https://skia-review.googlesource.com/103081
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed