fix(slide-toggle): thumb animation not working on mobile (#15236)
fix(slide-toggle): thumb animation not working on mobile (#15236)

With https://github.com/angular/material2/commit/cc8f871e8d3978cca95bffb3c0ab0d79961a8ddd, we enabled the `grabbing` cursor if the thumb container is pressed. This accidentally broke animation for the thumb sometimes because the `:active`
pseudo class is added on tap/touch and now accidentally sets the thumb transition duration to `0ms`. Rather we should only set the thumb transition duration to `0ms` if the user started dragging the thumb (with a small threshold)

Fixes #15232
Jefiozie/material2,crisbeto/material2,andrewseguin/material2,Jefiozie/material2,jelbourn/material2,josephperrott/material2,angular/components,crisbeto/material2,angular/components,DevVersion/material2,andrewseguin/material2,crisbeto/material2,DevVersion/material2,angular/components,jelbourn/material2,mmalerba/material2,Jefiozie/material2,jelbourn/material2,mmalerba/material2,jelbourn/material2,andrewseguin/material2,angular/components,crisbeto/material2,DevVersion/material2,josephperrott/material2,mmalerba/material2,mmalerba/material2,mmalerba/material2,Jefiozie/material2,DevVersion/material2,Jefiozie/material2,andrewseguin/material2,josephperrott/material2,jelbourn/material2,DevVersion/material2,josephperrott/material2,andrewseguin/material2,josephperrott/material2