Don't use gl_FragCoord on legacy Tegra hardware

Bug: skia:7413
Bug: skia:7757
Change-Id: I588c49409fd630f4c15546d8be64fb46c87db3c3
Reviewed-on: https://skia-review.googlesource.com/117007
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
4 files changed