Ensure that SwipeDismissBehavior affects the correct view

Can cause weirdness if there are views in the same location
as the Snackbar when it's being dragged. We now have a
callback in SwipeDismissBehavior to allow behaviors
to control which views can be dragged.

BUG: 24956960
BUG: 23756487
Change-Id: Idf82de127597eba3a543f99ffc2a088fbc9d3af0
3 files changed