Fix shader linker errors on several GL benchmarks

These were using an obsolete shader caps bit to manaully declare their
own FP output variable. That led to two outputs (after SkSL added
sk_FragColor), which led to errors about multiple outputs being declared
(without specifying location). SkSL handles all of this, so just use
sk_FragColor directly.

Bug: skia:
Change-Id: Id38657b6bf8c63c8f80d6ae3354a1507734a209f
Reviewed-on: https://skia-review.googlesource.com/73344
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
3 files changed