Allow ConstructorSplat to accept a scalar dest type.

Since the input must be a scalar argument of equivalent type, this is
just a no-op cast in practice (`float` to `float`, `int` to `int`). It
is harmless to allow it, and allows some call sites to be simplified.

Change-Id: I5a1a213fa3cf8c4afaabbbce3b34ab504792a267
Bug: skia:11032
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/392340
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
3 files changed