Demonstrate error with interface blocks.

We don't put interface block names in the symbol table. This means we
can add functions with the same name as an interface block, or have
two interface blocks with the same name, and no error is reported.

I added some non-code to main() to induce an error; otherwise we will
fail the SkSLError tests (which enforce that everything in errors/
must trigger at least one error).

Change-Id: Ic206116995d5f4ea3433b59d30c9744ce301990c
Bug: skia:13820
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/592379
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
3 files changed