Created attachment 196470 [details]
Test with html5:dialog and css-regions enabled.
Placing a dialog element inside a named flow, either by using the '-webkit-flow-into:' style property or by nesting it inside another flowed element will result in the <dialog> element not being displayed at all.
Testing was done on Chrome Canary as support for <dialog> tag in WebKit Safari is not yet fully exposed.
<dialog> bits have been removed from WebKit.