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

webrtc/p2p/base/transport.h

 /*
  *  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 134 matching lines @@
 // TODO(hta): Consider if a simple vector is as good as a map.
 typedef std::vector<TransportChannelStats> TransportChannelStatsList;
 
 // Information about the stats of a transport.
 struct TransportStats {
   std::string transport_name;
   TransportChannelStatsList channel_stats;
 };
 
 // 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;
   // Time interval in milliseconds to ping a backup connection when the ICE
   // channel is strongly connected.
   int backup_connection_ping_interval = -1;
   // If true, the most recent port allocator session will keep on running.
   bool gather_continually = false;
 
   // Whether we should prioritize Relay/Relay candidate when nothing
   // is writable yet.
   bool prioritize_most_likely_candidate_pairs = false;
 
   // If the current best connection is both writable and receiving,
   // then we will also try hard to make sure it is pinged at this rate
   // (Default value is a little less than 2 * STRONG_PING_INTERVAL).
   int max_strong_interval = -1;
 
+  // If set to false, this means the ICE transport can expect TURN-to-TURN
+  // candidate pairs to work even before CreatePermission requests are sent
+  // to the TURN servers. This allows media to be sent earlier, without even
+  // requiring binding request/responses to verify that the connection works.
+  bool fully_relayed_createpermission_needed = true;

[pthatcher1, 2016/06/21 06:20:50]

I still think this needs to reflect that we are opting into "presume
writability" territory.  

"presume_writability_when_fully_relayed" or something like that.

[Taylor Brandstetter, 2016/06/22 00:37:07]

Done.

+
   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 fully_relayed_no_createpermission_needed)
       : 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),
+        fully_relayed_createpermission_needed(
+            fully_relayed_no_createpermission_needed) {}
 };
 
 bool BadTransportDescription(const std::string& desc, std::string* err_desc);
 
 bool IceCredentialsChanged(const std::string& old_ufrag,
                            const std::string& old_pwd,
                            const std::string& new_ufrag,
                            const std::string& new_pwd);
 
 class Transport : public sigslot::has_slots<> {
@@ skipping 173 matching lines @@
 
   ChannelMap channels_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(Transport);
 };
 
 
 }  // namespace cricket
 
 #endif  // WEBRTC_P2P_BASE_TRANSPORT_H_