[skottie] Use animator scratch storage to avoid vector reallocations

Change-Id: Iab01c84ab83666218aa5ebc88f0d81b330858a74
Reviewed-on: https://skia-review.googlesource.com/145724
Commit-Queue: Florin Malita <fmalita@chromium.org>
Reviewed-by: Mike Reed <reed@google.com>
3 files changed