[skottie] plumb vec2 support to SlotManager

Change-Id: I8029b2b05b4d42b4844a0b664607762be253010b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/723336
Reviewed-by: Florin Malita <fmalita@google.com>
Commit-Queue: Jorge Betancourt <jmbetancourt@google.com>
4 files changed