Simplify IRGenerator::coerce.

I started unpacking the mechanics of type coercion, and realized that
the second half of the function was looking up the Symbol for a Type
based on its name (Types are already Symbols), converting that Symbol
back into a Type (we started with a Type anyway), wrapping that Type
in a TypeReference, then calling that TypeReference (which always
calls convertConstructor).

This CL cuts out the middle steps and simply calls convertConstructor
directly. A test was added to confirm that an earlier error encountered
on the CQ is no longer occurring.

Change-Id: I76aae455a301afe4e67ef989d9dfe11f47ed36ae
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/353105
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
6 files changed