Adding IceConfig option to assume TURN/TURN candidate pairs will work.

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 9b6cf519f89106885da65972fd605d1f6beb1766..fe82c2ffba9e3fe65eb13575336948d0ce50a028 100644
--- a/webrtc/p2p/base/transport.h
+++ b/webrtc/p2p/base/transport.h
@@ -152,6 +152,8 @@ struct TransportStats {
 };
 
 // Information about ICE configuration.
+// TODO(deadbeef): Use rtc::Optional to represent unset values, instead of
+// -1.
 struct IceConfig {
   // The ICE connection receiving timeout value in milliseconds.
   int receiving_timeout = -1;
@@ -170,18 +172,25 @@ struct IceConfig {
   // (Default value is a little less than 2 * STRONG_PING_INTERVAL).
   int max_strong_interval = -1;
 
+  // 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;
+
   IceConfig() {}
   IceConfig(int receiving_timeout_ms,
             int backup_connection_ping_interval,
             bool gather_continually,
             bool prioritize_most_likely_candidate_pairs,
-            int max_strong_interval_ms)
+            int max_strong_interval_ms,
+            bool presume_writable_when_fully_relayed)
       : receiving_timeout(receiving_timeout_ms),
         backup_connection_ping_interval(backup_connection_ping_interval),
         gather_continually(gather_continually),
         prioritize_most_likely_candidate_pairs(
             prioritize_most_likely_candidate_pairs),
-        max_strong_interval(max_strong_interval_ms) {}
+        max_strong_interval(max_strong_interval_ms),
+        presume_writable_when_fully_relayed(
+            presume_writable_when_fully_relayed) {}
 };
 
 bool BadTransportDescription(const std::string& desc, std::string* err_desc);