[whatwg] hit regions: type of events that are intercepted

[Rik Cabanier]

The current hit region specification doesn't state what events are routed
to the fallback content.
Probably only mouse and touch events should be intercepted and forwarded.

Thinking a bit more about this feature, it's a bit weird how events are
rerouted. Does this happen in any other place in the browser?
For instance, if the fallback is an edit control and the user drag-selects
some text on the canvas, is it expected that this text is also selected in
the edit control?