Add signaling to support ICE renomination.

webrtc/p2p/base/transport.h

Index: webrtc/p2p/base/transport.h
diff --git a/webrtc/p2p/base/transport.h b/webrtc/p2p/base/transport.h
index c2767fb6f0b43c8d7138002953b4dc282b0f7b13..ecca82e25a9c72a3a82019b6a2b3df5a0d2a2c44 100644
--- a/webrtc/p2p/base/transport.h
+++ b/webrtc/p2p/base/transport.h
@@ -212,6 +212,10 @@ struct IceConfig {
   // Default nomination mode if the remote does not support renomination.
   NominationMode default_nomination_mode = NominationMode::SEMI_AGGRESSIVE;
 
+  // If set to true, if the remote side supports ICE renomination, we will use
+  // renomination (if this side has the controlling role).
+  bool use_renomination_if_remote_supports = false;

[Taylor Brandstetter, 2016/08/08 22:28:16]

Why not just use `SetIceParameters` with `renomination` set to true for this
functionality? In fact, that's really what we *should* do, because if you SDP
munge to remove the "renomination" ICE option from the local description, we
shouldn't use renomination.

[honghaiz3, 2016/08/11 04:57:57]

So we will have a single control to control both 
1. Whether we support ICE renomination. 
2. Whether we will use ICE renomination if the remote supports. 
It makes sense to me. We don't need two control knobs for them. 

+
   IceConfig() {}
   IceConfig(int receiving_timeout_ms,
             int backup_connection_ping_interval,