Suppose the following case:
<div id='fallback'>fallback which is not used.</div>
If we click '#fallback' element, an event listener on #shadow-host can see #fallback element through event.target, which breaks an upper boundary of Shadow DOM.
Created attachment 148368 [details]
Comment on attachment 148368 [details]
Clearing flags on attachment: 148368
Committed r120754: <http://trac.webkit.org/changeset/120754>
All reviewed patches have been landed. Closing bug.