mdMenu sometimes blocks the entire screen #3892
Description
I managed to reproduce this on the Angular Material demo site as well (see screenshot).
When clicking on the menu sometimes it creates a md-backdrop element upon opening. This element covers everything and you cannot click anything anymore.
I saw this bug was reported a few times ago as well. Seems it's still there.
I manage to reproduce it in the rc3 version as well as the head version.
Steps to reproduce: just keep clicking an icon (i was clicking on the width="4" one on the bottom of the demo page). Once the menu opens, close it by clicking outside the menu. Do this a few times and the UI will be blocked by the md-menu-backdrop.
On the Angular Material demo site it happens rarely. On the site I'm working on it happens quite often (in 50% of cases cca).
Testing was done on Chrome v44.