we now complain if an SkSL program tries to override the default output

Bug: skia:
Change-Id: I387ddc3aac0712eb6c0a6ea39e48e5f3d809bc48
Reviewed-on: https://skia-review.googlesource.com/114691
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
2 files changed