[skottie] Add transform tracking to SkottieSlide

Add UI options to select a named transform for tracking, and render a
decoration to highlight the transformed origin.

Change-Id: I2a51278150e7098034e1f6e00b268fce69558b44
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/531551
Reviewed-by: Jorge Betancourt <jmbetancourt@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@google.com>
3 files changed