Fix cases of variable shadowing in SkSL.

Change-Id: I83aec4a2f65fe34b79ecc292131feb4027ce4bd4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/313139
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
8 files changed