Use ConstructorCompound::Make when optimizing swizzles.

Constructor::Convert is a very heavy hammer which does error-checking
and lots of logic to identify the right constructor type to use. It cuts
out a lot of redundant work to call the desired method
`ConstructorCompound::Make` directly instead.

Change-Id: Icf9e513dbce223c2b27ccd0d11dc08eea849ff39
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/539821
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
2 files changed