Stop events occuring in input fields when using a shadow DOM

[robinsk]

I'm using Mousetrap with Polymer, and I just noticed that events in inputs aren't stopped by default. The reason for this is that Mousetrap uses target or srcElement in the stopCallback function, but when the event occurs in a shadow DOM, the events are retargeted to look like they come from the host element.

A fix would be to use the first element from the event path if event.path is available.

[ccampbell]

I'd be happy to fix this... Do you have an example or test that I could use?