Add a switch to redetermine role when ICE restarts.

webrtc/api/peerconnectioninterface.h

Index: webrtc/api/peerconnectioninterface.h
diff --git a/webrtc/api/peerconnectioninterface.h b/webrtc/api/peerconnectioninterface.h
index fdf9cef51ec2a2a8b419227522d085a36b2c4ad2..548ea5101ed711c392e158c26984c0beb7cea3b7 100644
--- a/webrtc/api/peerconnectioninterface.h
+++ b/webrtc/api/peerconnectioninterface.h
@@ -240,6 +240,12 @@ class PeerConnectionInterface : public rtc::RefCountInterface {
     // methods for all settings which are of interest to applications,
     // Chrome in particular.
 
+    static RTCConfiguration NativeConfiguration() {

[pthatcher1, 2016/08/30 20:25:36]

Can we call this OptimalConfiguration()?

And have a SafeConfiguration()?

And have comments for each of them describing when one should use one and one
should use the other?

[honghaiz3, 2016/08/30 21:32:59]

Done. Is it better to call it ExperiementalConfiguration, which is more like an
opposite to SafeConfiguration?

+      RTCConfiguration config;
+      config.redetermine_role_on_ice_restart = false;

[pthatcher1, 2016/08/30 20:25:36]

Can you also enable things like max_bundle, required rtcp_mux, and continual
gathering?

[honghaiz3, 2016/08/30 21:32:59]

Will do this in a separate CL as discussed. 

+      return config;
+    }
+
     bool dscp() { return media_config.enable_dscp; }
     void set_dscp(bool enable) { media_config.enable_dscp = enable; }
 
@@ -305,6 +311,9 @@ class PeerConnectionInterface : public rtc::RefCountInterface {
     // If set to true, this means the ICE transport should presume TURN-to-TURN
     // candidate pairs will succeed, even before a binding response is received.
     bool presume_writable_when_fully_relayed = false;
+    // If true, ICE role is redetermined when peerconnection sets a local
+    // transport description that indicates an ICE restart.
+    bool redetermine_role_on_ice_restart = true;
   };
 
   struct RTCOfferAnswerOptions {