Add animated cowboy sample from WebKit tests, and fix.

Bug: chromium:712455
Change-Id: Ic9bb9b862abe01f112cc41d28589733460b15bc1
Reviewed-on: https://skia-review.googlesource.com/50181
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
2 files changed