Change the gating of surfacing candidates on ICE transport type change
from a field trial to RTCConfiguration.

The test coverage is also expanded for the underlying feature.

Bug: None
Change-Id: Ic9c1362867e4a956c5453be7a9355083b6a442f5
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/138980
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Reviewed-by: Alex Glaznev <glaznev@webrtc.org>
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Amit Hilbuch <amithi@webrtc.org>
Commit-Queue: Qingsi Wang <qingsi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28143}
diff --git a/pc/peer_connection_integrationtest.cc b/pc/peer_connection_integrationtest.cc
index 7b3163b..395c437 100644
--- a/pc/peer_connection_integrationtest.cc
+++ b/pc/peer_connection_integrationtest.cc
@@ -5086,8 +5086,6 @@
 }
 
 TEST_P(PeerConnectionIntegrationTest, RegatherAfterChangingIceTransportType) {
-  webrtc::test::ScopedFieldTrials field_trials(
-      "WebRTC-GatherOnCandidateFilterChanged/Enabled/");
   static const rtc::SocketAddress turn_server_internal_address{"88.88.88.0",
                                                                3478};
   static const rtc::SocketAddress turn_server_external_address{"88.88.88.1", 0};
@@ -5103,11 +5101,13 @@
   caller_config.servers.push_back(ice_server);
   caller_config.type = webrtc::PeerConnectionInterface::kRelay;
   caller_config.continual_gathering_policy = PeerConnection::GATHER_CONTINUALLY;
+  caller_config.surface_ice_candidates_on_ice_transport_type_changed = true;
 
   PeerConnectionInterface::RTCConfiguration callee_config;
   callee_config.servers.push_back(ice_server);
   callee_config.type = webrtc::PeerConnectionInterface::kRelay;
   callee_config.continual_gathering_policy = PeerConnection::GATHER_CONTINUALLY;
+  callee_config.surface_ice_candidates_on_ice_transport_type_changed = true;
 
   ASSERT_TRUE(
       CreatePeerConnectionWrappersWithConfig(caller_config, callee_config));