Add viewer GUI options for desktop and Android to toggle instanced rendering.

BUG=skia:

Change-Id: I42674abfb7ee764f676100ac0e84cc0f07620bec
Reviewed-on: https://skia-review.googlesource.com/9396
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
1 file changed