On the demo page, we use the skia-cdn bucket to hopefully
have better performance than unpkg.
Additionally, on the demo page, we default to using the
WASM version if supported by the browser.
Docs-Preview: https://skia.org/?cl=150904
Bug: skia:8216
Change-Id: I901016e95b8d66803053680691aac4d314821d18
Reviewed-on: https://skia-review.googlesource.com/150904
Reviewed-by: Joe Gregorio <jcgregorio@google.com>