Uses a new GPU sink that runs each test twice, once to populate the
cache and then again with a new GrContext but a warmed cache. It
verifies that the two generated images are the same.
Change-Id: Iaba195a69751f14ea946afe7174228a813b83a63
Reviewed-on: https://skia-review.googlesource.com/140567
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
