Added multi-var variants for the DSL Declare function

Change-Id: I84fe0319a15065f5de85cd4bed20d648b88c2b56
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/429897
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
3 files changed