The WMS used in the example does not send CORS headers (I think
not many WMS services do). It seems that the WebGL renderer
needs script access to the image data, so the example only works
with the DOM renderer in Firefox.
This ensures that maps with WMS layers with different extents
do not scale the tiles differently for each layer when the
default tileGrid is used. Note that it is always possible to
configure WMS sources with a custom tileGrid.
The [URI standard](http://tools.ietf.org/html/rfc3986#section-4.2)
allows for URI without a scheme. Where http is used to load the app,
using a schemeless URL for the Bing metadata loads a script using http
- and the same goes for https.
