Unlike the WebRtcMessageListener, which is bound to a specific peer
connection, an OfferMessageListener listens to all offer messages, no
matter which peer connection they are bound to. This can be used, for
example, to create a new peer connection when a remote offer for which
there is no previous connection is received.
Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>
