SVGPong relies on onOnceBeforeDraw() to initialize, but when switching
slides via Viewer's UI, onAnimate() is fired before the first paint.
Change-Id: I7be133072ec635975f7463538cd42edb69696b3f
Reviewed-on: https://skia-review.googlesource.com/79424
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>