fix(overlay): backdrop exit animation not working (#10145)
fix(overlay): backdrop exit animation not working (#10145)

Fixes the transition when closing an overlay with an opaque backdrop appearing broken. The issue comes the fact that when we start animating the backdrop out, we also remove the `backdropClass` which makes the backdrop transparent. We don't need to remove the class, because we'll remove the backdrop from the DOM and clear the reference once the transition is done.
jelbourn/material2,angular/components,jelbourn/material2,mmalerba/material2,andrewseguin/material2,crisbeto/material2,mmalerba/material2,jelbourn/material2,mmalerba/material2,jelbourn/material2,DevVersion/material2,angular/components,mmalerba/material2,DevVersion/material2,crisbeto/material2,DevVersion/material2,josephperrott/material2,andrewseguin/material2,Jefiozie/material2,crisbeto/material2,DevVersion/material2,Jefiozie/material2,Jefiozie/material2,andrewseguin/material2,josephperrott/material2,josephperrott/material2,jelbourn/material2,Jefiozie/material2,andrewseguin/material2,josephperrott/material2,andrewseguin/material2,angular/components,Jefiozie/material2,DevVersion/material2,mmalerba/material2,angular/components,josephperrott/material2,crisbeto/material2