Fix handling of rejected m-lines without transport description

A fingerprint should not be required for m-lines which are rejected.

BUG=chromium:326493639,webrtc:11066

Change-Id: I7428c91a144ca46650e13d72868f160652a98339
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/340322
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Commit-Queue: Philipp Hancke <phancke@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#41794}

pc/media_session.cc

diff --git a/pc/media_session.cc b/pc/media_session.cc
index 4f63f30..3928088 100644
--- a/pc/media_session.cc
+++ b/pc/media_session.cc
@@ -2174,12 +2174,12 @@
   }
   // If this section is part of a bundle, bundle_transport is non-null.
   // Then require_transport_attributes is false - we can handle sections
-  // without the DTLS parameters. Otherwise, transport attributes MUST
-  // be present.
+  // without the DTLS parameters. For rejected m-lines it does not matter.
+  // Otherwise, transport attributes MUST be present.
   std::unique_ptr<TransportDescription> transport = CreateTransportAnswer(
       media_description_options.mid, offer_description,
       media_description_options.transport_options, current_description,
-      bundle_transport == nullptr, ice_credentials);
+      !offer_content->rejected && bundle_transport == nullptr, ice_credentials);
   if (!transport) {
     LOG_AND_RETURN_ERROR(
         RTCErrorType::INTERNAL_ERROR,
@@ -2272,7 +2272,7 @@
   std::unique_ptr<TransportDescription> data_transport = CreateTransportAnswer(
       media_description_options.mid, offer_description,
       media_description_options.transport_options, current_description,
-      bundle_transport != nullptr, ice_credentials);
+      !offer_content->rejected && bundle_transport == nullptr, ice_credentials);
   if (!data_transport) {
     LOG_AND_RETURN_ERROR(
         RTCErrorType::INTERNAL_ERROR,
@@ -2344,10 +2344,11 @@
     SessionDescription* answer,
     IceCredentialsIterator* ice_credentials) const {
   std::unique_ptr<TransportDescription> unsupported_transport =
-      CreateTransportAnswer(media_description_options.mid, offer_description,
-                            media_description_options.transport_options,
-                            current_description, bundle_transport != nullptr,
-                            ice_credentials);
+      CreateTransportAnswer(
+          media_description_options.mid, offer_description,
+          media_description_options.transport_options, current_description,
+          !offer_content->rejected && bundle_transport == nullptr,
+          ice_credentials);
   if (!unsupported_transport) {
     LOG_AND_RETURN_ERROR(
         RTCErrorType::INTERNAL_ERROR,