Improved DSLType constructor signatures

Being able to Construct() arbitrary types is necessary for the upcoming
DSLParser.

Change-Id: I2d439b4a1db7a460043efa5f0e9207b6073e9f1f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/403696
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
2 files changed