Implement array-cast constructors in WGSL.

Since WGSL 1.0 does not have precision qualifiers or support for
half types, this is a no-op.

Change-Id: Iff039583f8e91f5ef2e56250ee22b66844996ac2
Bug: skia:14082
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/716998
Reviewed-by: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
4 files changed