Revert "Implement true negotiation for DatagramTransport with fallback to RTP."

This reverts commit 71c6482baf0ff17141c635e6a7639493db68a65c.

Reason for revert: Lands too much at once and breaks downstream tests that need to implement new interfaces first.

Original change's description:
> Implement true negotiation for DatagramTransport with fallback to RTP.
> 
> In short, the caller places a x-opaque line in SDP for each m= section that
> uses datagram transport.  If the answerer supports datagram transport, it will
> parse this line and create a datagram transport.  It will then echo the x-opaque
> line into the answer (to indicate that it accepted use of datagram transport).
> 
> If the offer and answer contain exactly the same x-opaque line, both peers will
> use datagram transport.  If the x-opaque line is omitted from the answer (or is
> different in the answer) they will fall back to RTP.
> 
> Note that a different x-opaque line in the answer means the answerer did not
> understand something in the negotiation proto.  Since WebRTC cannot know what
> was misunderstood, or whether it's still possible to use the datagram transport,
> it must fall back to RTP.  This may change in the future, possibly by passing
> the answer to the datagram transport, but it's good enough for now.
> 
> Negotiation consists of four parts:
>  1. DatagramTransport exposes transport parameters for both client and server
>  perspectives.  The client just echoes what it received from the server (modulo
>  any fields it might not have understood).
> 
>  2. SDP adds a x-opaque line for opaque transport parameters.  Identical to
>  x-mt, but this is specific to datagram transport and goes in each m= section,
>  and appears in the answer as well as the offer.
>   - This is propagated to Jsep as part of the TransportDescription.
>   - SDP files: transport_description.h,cc, transport_description_factory.h,cc,
>     media_session.cc, webrtc_sdp.cc
> 
>  3. JsepTransport/Controller:
>   - Exposes opaque parameters for each mid (m= section).  On offerer, this means
>     pre-allocating a datagram transport and getting its parameters.  On the
>     answerer, this means echoing the offerer's parameters.
>   - Uses a composite RTP transport to receive from either default RTP or
>     datagram transport until both offer and answer arrive.
>   - If a provisional answer arrives, sets the composite to send on the
>     provisionally selected transport.
>   - Once both offer and answer are set, deletes the unneeded transports and
>     keeps whichever transport is selected.
> 
>  4. PeerConnection pulls transport parameters out of Jsep and adds them to SDP.
> 
> Bug: webrtc:9719
> Change-Id: Id8996eb1871e79d93b7923a5d7eb3431548c798d
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/140700
> Commit-Queue: Bjorn Mellem <mellem@webrtc.org>
> Reviewed-by: Steve Anton <steveanton@webrtc.org>
> Reviewed-by: Anton Sukhanov <sukhanov@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#28182}

TBR=steveanton@webrtc.org,mellem@webrtc.org,sukhanov@webrtc.org

Change-Id: I0d502c4a6d27516c35ed85154f3fa5869f88b3b7
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:9719
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/140822
Commit-Queue: Bjorn Mellem <mellem@webrtc.org>
Reviewed-by: Bjorn Mellem <mellem@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28188}

1 files changed, 0 insertions, 3 deletions

diff --git a/pc/media_session.cc b/pc/media_session.cc
index f989d28f72..fe11d44702 100644
--- a/pc/media_session.cc
+++ b/pc/media_session.cc
@@ -540,15 +540,12 @@ static bool UpdateTransportInfoForBundle(const ContentGroup& bundle_group,
       selected_transport_info->description.ice_pwd;
   ConnectionRole selected_connection_role =
       selected_transport_info->description.connection_role;
-  const absl::optional<OpaqueTransportParameters>& selected_opaque_parameters =
-      selected_transport_info->description.opaque_parameters;
   for (TransportInfo& transport_info : sdesc->transport_infos()) {
     if (bundle_group.HasContentName(transport_info.content_name) &&
         transport_info.content_name != selected_content_name) {
       transport_info.description.ice_ufrag = selected_ufrag;
       transport_info.description.ice_pwd = selected_pwd;
       transport_info.description.connection_role = selected_connection_role;
-      transport_info.description.opaque_parameters = selected_opaque_parameters;
     }
   }
   return true;