[Events] Determining the Event Receiver

New additions:

> The receiver attribute of each instance of the UIRequestEvent interface must return an EventTarget matching the DOMElement where the corresponding event's action is declared via the uiactions attribute.

> 3.1.2 Determining the Event Receiver
> 
> The event receiver is determined using the following steps:
> 
> For each event name literal (e.g. "dismissrequest"), determine the corresponding uiactions token (e.g. "dismiss").
> Starting with the event's target element, determine if the element's actions list contains the corresponding action for the event (e.g.el.uiactions.contains("dismiss")). If the current element's action list contains the corresponding uiactions token, the event target is also the event receiver.
> If the current element's action list does not contain the corresponding uiactions token, move up to the parent element and try again. Continue until reaching the root element. The closest ancestor to match the corresponding action token is the event receiver.
> If the event receiver is still undetermined upon reaching the root element, stop. There is no valid event receiver and the user agent must not initiate the event.


Link
https://dvcs.w3.org/hg/IndieUI/raw-file/default/src/indie-ui-events.html#UIRequestEvent

Changeset
https://dvcs.w3.org/hg/IndieUI/rev/10e0d452f2e1