Delete deprecated disable_ipv6 flag.

M108 Stable has been released, which does not contain googIPv6 anymore,
and today the last downstream dependency on this flag was removed.

Let's delete!

Bug: webrtc:14608
Change-Id: Ia2d201f0da04b14961f891687b6135fc69b7767e
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/285720
Auto-Submit: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Henrik Boström <hbos@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#38786}
diff --git a/api/peer_connection_interface.h b/api/peer_connection_interface.h
index d89b226..1097a16 100644
--- a/api/peer_connection_interface.h
+++ b/api/peer_connection_interface.h
@@ -426,13 +426,6 @@
     // default will be used.
     //////////////////////////////////////////////////////////////////////////
 
-    // If set to true, don't gather IPv6 ICE candidates.
-    // TODO(https://crbug.com/webrtc/14608): Delete this flag.
-    union {
-      bool DEPRECATED_disable_ipv6 = false;
-      bool ABSL_DEPRECATED("https://crbug.com/webrtc/14608") disable_ipv6;
-    };
-
     // If set to true, don't gather IPv6 ICE candidates on Wi-Fi.
     // Only intended to be used on specific devices. Certain phones disable IPv6
     // when the screen is turned off and it would be better to just disable the
diff --git a/pc/peer_connection.cc b/pc/peer_connection.cc
index 0340866..5f6016a 100644
--- a/pc/peer_connection.cc
+++ b/pc/peer_connection.cc
@@ -297,7 +297,6 @@
     RtcpMuxPolicy rtcp_mux_policy;
     std::vector<rtc::scoped_refptr<rtc::RTCCertificate>> certificates;
     int ice_candidate_pool_size;
-    bool DEPRECATED_disable_ipv6;
     bool disable_ipv6_on_wifi;
     int max_ipv6_networks;
     bool disable_link_local_networks;
@@ -367,7 +366,6 @@
          prioritize_most_likely_ice_candidate_pairs ==
              o.prioritize_most_likely_ice_candidate_pairs &&
          media_config == o.media_config &&
-         DEPRECATED_disable_ipv6 == o.DEPRECATED_disable_ipv6 &&
          disable_ipv6_on_wifi == o.disable_ipv6_on_wifi &&
          max_ipv6_networks == o.max_ipv6_networks &&
          disable_link_local_networks == o.disable_link_local_networks &&
@@ -2116,11 +2114,7 @@
   port_allocator_flags |= cricket::PORTALLOCATOR_ENABLE_SHARED_SOCKET |
                           cricket::PORTALLOCATOR_ENABLE_IPV6 |
                           cricket::PORTALLOCATOR_ENABLE_IPV6_ON_WIFI;
-  // If the disable-IPv6 flag was specified, we'll not override it
-  // by experiment.
-  if (configuration.DEPRECATED_disable_ipv6) {
-    port_allocator_flags &= ~(cricket::PORTALLOCATOR_ENABLE_IPV6);
-  } else if (trials().IsDisabled("WebRTC-IPv6Default")) {
+  if (trials().IsDisabled("WebRTC-IPv6Default")) {
     port_allocator_flags &= ~(cricket::PORTALLOCATOR_ENABLE_IPV6);
   }
   if (configuration.disable_ipv6_on_wifi) {
diff --git a/pc/peer_connection_interface_unittest.cc b/pc/peer_connection_interface_unittest.cc
index 71d6f0c..dfca486 100644
--- a/pc/peer_connection_interface_unittest.cc
+++ b/pc/peer_connection_interface_unittest.cc
@@ -1334,7 +1334,6 @@
   server.uri = kStunAddressOnly;
   config.servers.push_back(server);
   config.type = PeerConnectionInterface::kRelay;
-  config.DEPRECATED_disable_ipv6 = true;
   config.tcp_candidate_policy =
       PeerConnectionInterface::kTcpCandidatePolicyDisabled;
   config.candidate_network_policy =
@@ -1347,7 +1346,6 @@
           port_allocator_->GetPooledSession());
   ASSERT_NE(nullptr, session);
   EXPECT_EQ(1UL, session->stun_servers().size());
-  EXPECT_EQ(0U, session->flags() & cricket::PORTALLOCATOR_ENABLE_IPV6);
   EXPECT_LT(0U, session->flags() & cricket::PORTALLOCATOR_DISABLE_TCP);
   EXPECT_LT(0U,
             session->flags() & cricket::PORTALLOCATOR_DISABLE_COSTLY_NETWORKS);
@@ -3828,10 +3826,6 @@
   f.ice_connection_receiving_timeout = 1337;
   EXPECT_NE(a, f);
 
-  PeerConnectionInterface::RTCConfiguration g;
-  g.DEPRECATED_disable_ipv6 = true;
-  EXPECT_NE(a, g);
-
   PeerConnectionInterface::RTCConfiguration h(
       PeerConnectionInterface::RTCConfigurationType::kAggressive);
   EXPECT_NE(a, h);