Add parameter to TransportController to not change ICE role on restart.

webrtc/p2p/base/transportcontroller.cc

Index: webrtc/p2p/base/transportcontroller.cc
diff --git a/webrtc/p2p/base/transportcontroller.cc b/webrtc/p2p/base/transportcontroller.cc
index b5021cceccb73c18592b7a8f8bd7d97861e09cce..ec4c3f129307cf37c097472e0d6b63a97ef48eda 100644
--- a/webrtc/p2p/base/transportcontroller.cc
+++ b/webrtc/p2p/base/transportcontroller.cc
@@ -44,10 +44,20 @@ struct CandidatesData : public rtc::MessageData {
 
 TransportController::TransportController(rtc::Thread* signaling_thread,
                                          rtc::Thread* network_thread,
-                                         PortAllocator* port_allocator)
+                                         PortAllocator* port_allocator,
+                                         bool redetermine_role_on_ice_restart)
     : signaling_thread_(signaling_thread),
       network_thread_(network_thread),
-      port_allocator_(port_allocator) {}
+      port_allocator_(port_allocator),
+      redetermine_role_on_ice_restart_(redetermine_role_on_ice_restart) {}
+
+TransportController::TransportController(rtc::Thread* signaling_thread,
+                                         rtc::Thread* network_thread,
+                                         PortAllocator* port_allocator)
+    : TransportController(signaling_thread,
+                          network_thread,
+                          port_allocator,
+                          true) {}
 
 TransportController::~TransportController() {
   network_thread_->Invoke<void>(
@@ -448,11 +458,12 @@ bool TransportController::SetLocalTransportDescription_n(
 
   // Older versions of Chrome expect the ICE role to be re-determined when an
   // ICE restart occurs, and also don't perform conflict resolution correctly,
-  // so for now we can't safely stop doing this.
+  // so for now we can't safely stop doing this, unless the application opts in
+  // by setting |redetermine_role_on_ice_restart_| to false.
   // See: https://bugs.chromium.org/p/chromium/issues/detail?id=628676
   // TODO(deadbeef): Remove this when these old versions of Chrome reach a low
   // enough population.
-  if (transport->local_description() &&
+  if (redetermine_role_on_ice_restart_ && transport->local_description() &&
       IceCredentialsChanged(transport->local_description()->ice_ufrag,
                             transport->local_description()->ice_pwd,
                             tdesc.ice_ufrag, tdesc.ice_pwd)) {