Support sample coords in .fp main()

This removes the code generation support for @coordTransform and sk_TransformedCoords2D
when processing .fp files. Instead, the main() function can optionally add a float2
parameter. This is marked as the SK_MAIN_COORDS builtin, just like the main function
for a runtime pipeline stage.

Bug: skia:10416
Change-Id: I0c192d890bb798a1167bc445003f6ddffe6118f0
Reviewed-by: Brian Osman <>
Commit-Queue: Michael Ludwig <>
17 files changed