Whitney Houston's cause of death came out right in the middle of today's TMZ Live ... which means you get to see what happens as all the breaking details -- drowning, cocaine, heart problems -- come into the newsroom and get up on the site. Also, Justin Bieber joined us -- he's fighting to get "Bully" a PG-13 instead of an R. It's no worse than the violence in "The Hunger Games" ... right? We talked to the Biebs about the controversy. And a major twist in Lindsay Lohan's alleged hit and run case.