Fixed DSLParser code rot

Where DSLParser is #ifdef'ed out, it had experienced some code rot and
was no longer building. This fixes it to be able to successfully build
when SKSL_DSL_PARSER is set to 1.

Change-Id: I5846b05ba3342b5b1502663577663e332c55529b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/442976
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
9 files changed