Move fragCoord workaround declaration

This ensures that all extension directives occur before any
non-preprocessor tokens, as required by the spec (ยง 3.4).

This was found by Qualcomm, and originally submitted as
https://github.com/google/skia/pull/21

Bug: b/111525079
Change-Id: I24357e4d3654e76c2dfbc067aca3088948dfa5a8
Reviewed-on: https://skia-review.googlesource.com/142697
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed