Add WGSL support for struct constructors.

It looks as if the `assembleAnyConstructor` path already emitted
the perfect output for a struct ctor; we just needed to call it.

Change-Id: Ib0d6bd565ac8b4d20dee5d85f8743473c9747167
Bug: skia:14082
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/705078
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
5 files changed