Announcing the Presentation-Cast polyfill and slideshow demo

Francois, Dominik, group members,

I'm pleased to announce a (mostly-)complete polyfill [1] for the
Presentation API draft specification [2] using the Google Cast Sender SDK
for Chrome [3].  It includes a simple demo Web application starting and
controlling a photo slideshow [4].

This polyfill is more limited in scope than the slidyremote one published
earlier by Francois [5], but is more up-to-date with the current
specification.   It is only compatible with Cast devices and only
implements the opener/controller aspects of the Presentation API.

I plan to extend it to implement more of the API, including the joinSession
and presentation-side behaviors, and to have a fallback for those without
access to a Cast device.

I also plan to implement a prototype of a remotable <video> tag and a
multi-player game to help prototyping relevant aspects of the API.
Finally, it may be possible to prototype the 1-UA situation using the
tab-casting features of the Cast extension, but this will require some more
investigation.

Once the polyfill is more feature complete I hope we can use it to analyze
the current state of the specification.

m.

[1] https://github.com/mfoltzgoogle/presentation-cast
[2] http://w3c.github.io/presentation-api/
[3] https://developers.google.com/cast/docs/reference/chrome/
[4] https://mfoltzgoogle.github.io/presentation-cast/demo/slideshow/
[5] https://github.com/webscreens/slidyremote

P.S. In order to send messages from the presentation document back to the
controlling document, I needed to fork slidyremote and make a small patch
to the receiver shim [6].

[6] https://github.com/mfoltzgoogle/slidyremote