input event should use InputEvent

[domenic]

http://w3c.github.io/editing/input-events.html defines a new InputEvent type that it clearly intends to be used for the HTML input event defined in https://html.spec.whatwg.org/#event-input. However, it never defines the actual procedure by which these events are created or fired, or how their initialization values are determined. (It has some vague stuff like "A user agent MUST dispatch this event immediately after the DOM has been updated." but that clearly doesn't fit into the existing lifecycle; compare it to the spec's existing "Queue a task to fire a simple event that bubbles named input at the input element.") Furthermore, HTML currently says to dispatch a plain ol' Event.

It seems, based on blink-dev, there is public support for this change. We should update HTML.

See also #601.

[zcorpan]

cc @johanneswilm

[jimmywarting]

This is bugging me now that an InputEvent isn't triggered. It behaving differently on firefox and other browsers...
I'm using a Datalist as autocompletion, and whenever something is selected then i would like to know about it via InputEvent.prototype.inputType. I can't do that if a normal Event is dispatched. cuz Event dose not have inputType

Also if you click with a mouse (using chrome) to select something then it will dispatch a normal Event and fire the onkeydown handler. the event.type is still weirdly keydown. never was any keyboard button pressed while only using the mouse. Firefox don't trigger this onkeydown event when using the mouse

demo: https://jsfiddle.net/aLes7n6q/
chrome behaves weird, and triggers both event handlers,
I think Firefox got this right and it also uses inputType=insertReplacementText