[skottie] Animator tweaks

  * reserve SkPath storage to avoid incremental allocations
  * refactor eval() to avoid copying data when interpolation is not
    triggered

Change-Id: I467affbbfd652e8fa2a486acab7d6c7b9165d49f
Reviewed-on: https://skia-review.googlesource.com/146166
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
2 files changed