[skottie] Expose property bindings in CK

Add a new (optionally-built) ManagedAnimation CK helper, and provide
accessors for color and opacity properties.

The new wrapper class can be used as a drop-in replacement for the existing
Animation.

Change-Id: Iab6b6be9c736697b4731722806b145cbd130ce73
Reviewed-on: https://skia-review.googlesource.com/c/173322
Commit-Queue: Florin Malita <fmalita@chromium.org>
Reviewed-by: Kevin Lubick <kjlubick@google.com>
3 files changed