Update SkSL docs slightly

- Use .eval() in all example fiddles
- Add some more explanation of how the parts of a draw/paint contribute
  to the GPU fragment shader.

Bug: skia:12302
Change-Id: Ib69b9af39368c980e1aa9206af585f26498d083e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/445640
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
1 file changed