Add unit test for TraceHooks on compiled SkSL.

This verifies that compiled SkSL code generates a reasonable trace.

Change-Id: Ia81a694460eaac261dfb9287b64f0afec013f76c
Bug: skia:12614
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/473145
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
1 file changed