Surface the standardized ICE connection state to mobile clients.

This CL adds the callback on changes of the ICE connection state
following the standardized transitions
(https://www.w3.org/TR/webrtc/#dom-rtciceconnectionstate) to the
Android and the iOS SDKs.

Bug: None
Change-Id: I6133391fa54dd4e09016f29dddb85e4a0e270878
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/138181
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Reviewed-by: Amit Hilbuch <amithi@webrtc.org>
Reviewed-by: Alex Glaznev <glaznev@webrtc.org>
Commit-Queue: Qingsi Wang <qingsi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28127}

sdk/objc/api/peerconnection/RTCPeerConnection+Private.h

@@ -39,6 +39,9 @@ class PeerConnectionDelegateAdapter : public PeerConnectionObserver {
 
   void OnIceConnectionChange(PeerConnectionInterface::IceConnectionState new_state) override;
 
+  void OnStandardizedIceConnectionChange(
+      PeerConnectionInterface::IceConnectionState new_state) override;
+
   void OnConnectionChange(PeerConnectionInterface::PeerConnectionState new_state) override;
 
   void OnIceGatheringChange(PeerConnectionInterface::IceGatheringState new_state) override;

sdk/objc/api/peerconnection/RTCPeerConnection.h

@@ -126,6 +126,11 @@ RTC_OBJC_EXPORT
  *  This is only called with RTCSdpSemanticsUnifiedPlan specified.
  */
 @optional
+/** Called any time the IceConnectionState changes following standardized
+ * transition. */
+- (void)peerConnection:(RTCPeerConnection *)peerConnection
+    didChangeStandardizedIceConnectionState:(RTCIceConnectionState)newState;
+
 /** Called any time the PeerConnectionState changes. */
 - (void)peerConnection:(RTCPeerConnection *)peerConnection
     didChangeConnectionState:(RTCPeerConnectionState)newState;

sdk/objc/api/peerconnection/RTCPeerConnection.mm

@@ -179,6 +179,16 @@ void PeerConnectionDelegateAdapter::OnIceConnectionChange(
   [peer_connection_.delegate peerConnection:peer_connection_ didChangeIceConnectionState:state];
 }
 
+void PeerConnectionDelegateAdapter::OnStandardizedIceConnectionChange(
+    PeerConnectionInterface::IceConnectionState new_state) {
+  if ([peer_connection_.delegate
+          respondsToSelector:@selector(peerConnection:didChangeStandardizedIceConnectionState:)]) {
+    RTCIceConnectionState state = [RTCPeerConnection iceConnectionStateForNativeState:new_state];
+    [peer_connection_.delegate peerConnection:peer_connection_
+        didChangeStandardizedIceConnectionState:state];
+  }
+}
+
 void PeerConnectionDelegateAdapter::OnConnectionChange(
     PeerConnectionInterface::PeerConnectionState new_state) {
   if ([peer_connection_.delegate