Re: [gamepad] preventing default/capturing controller

Adding a best approach to the spec is a good idea.

Originally I thought that having a gamepadconnected callback (or some use
of the Gamepad API) would be enough of an indicator to prevent the UA from
manipulating the key presses / cursor movement.

The main scenarios I'm struggling to see as a good fit for this:

- The developer has a settings screen and would rather use the UA's
manipulated keys within an event listener, rather than handle gamepad state
in an animation frame. A separate API would probably be cleaner for
developers to follow and presumably easier to implement in the UA side.
- [Much more niche] There are native components around the edge of the UA
which could be interacted with, Firefox on the Ouya is a great example.
Should this be something which is catered for? Ideally the game would want
to be in fullscreen mode and the user would have to leave fullscreen to
interact with the native elements, this way the UA has a clear point to
break out of the gamepad mode.

I'll try and get hold of Scott Graham and see if he has any thoughts /
comments.