Add signaling to support ICE renomination.

webrtc/pc/mediasession.cc

 /*
  *  Copyright 2004 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 704 matching lines @@
   return false;
 }
 
 template <class C>
 static bool IsRtxCodec(const C& codec) {
   return stricmp(codec.name.c_str(), kRtxCodecName) == 0;
 }
 
 static TransportOptions GetTransportOptions(const MediaSessionOptions& options,
                                             const std::string& content_name) {
+  TransportOptions transport_options;
   auto it = options.transport_options.find(content_name);
-  if (it == options.transport_options.end()) {
-    return TransportOptions();
+  if (it != options.transport_options.end()) {
+    transport_options = it->second;
   }
-  return it->second;
+  transport_options.ice_renomination = options.ice_renomination;

[skvlad, 2016/08/26 23:59:10]

Is options.ice_renomination always supposed to override
transport_options.ice_renomination? In that case, what is the reason to keep
them separate?

[honghaiz3, 2016/08/29 18:52:52]

Good point. I think that is the reason I have not chosen this approach at the
initial version (see patch 10). 
The reason to keep two ice_renomination options which look redundant is that the
transport options are keyed by the content names, and when we set the transport
options, the content names may not be available yet (for the first offer, for
example). So it is safer to set the ice_renomination in the Session Option and
copy it over to the transport option when the content name is known. 

+  return transport_options;
 }
 
 // Create a media content to be offered in a session-initiate,
 // according to the given options.rtcp_mux, options.is_muc,
 // options.streams, codecs, secure_transport, crypto, and streams.  If we don't
 // currently have crypto (in current_cryptos) and it is enabled (in
 // secure_policy), crypto is created (according to crypto_suites).  If
 // add_legacy_stream is true, and current_streams is empty, a legacy
 // stream is created.  The created content is added to the offer.
 template <class C>
@@ skipping 1454 matching lines @@
       GetFirstMediaContentDescription(sdesc, MEDIA_TYPE_VIDEO));
 }
 
 DataContentDescription* GetFirstDataContentDescription(
     SessionDescription* sdesc) {
   return static_cast<DataContentDescription*>(
       GetFirstMediaContentDescription(sdesc, MEDIA_TYPE_DATA));
 }
 
 }  // namespace cricket