[DOM3Events] Bind to multimedia buttons

Hello everyone,

I've been working on writing up a use case for allowing documents to bind to events from physical keyboard multimedia buttons. The DOM Level 3 Events spec[1] currently has support for these buttons (in the sense that there are specific key identifiers for the buttons, namely MediaNextTrack, MediaPlayPause, MediaPreviousTrack, MediaStop[2]). However, there are a few problems that limit their use:

1. A document has to be in focus in order to capture a KeyboardEvent.
2. Multimedia button events often won't reach the browser, because the buttons are bound to other media players (e.g. iTunes on OS X, even if iTunes isn't running.)

I've written up a more detailed rationale and I'd greatly appreciate any feedback:

https://gist.github.com/joelcox/6641424

Joël

[1]: http://www.w3.org/TR/2003/NOTE-DOM-Level-3-Events-20031107/Overview.html
[2]: http://www.w3.org/TR/2003/NOTE-DOM-Level-3-Events-20031107/keyset.html#KeySet-Set