Expose PeerConnection.restartIce in iOS SDK.

Bug: None
Change-Id: I76b95b3182e6b384fd68aecf4210c23459f76d2b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/209709
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Commit-Queue: Yura Yaroshevich <yura.yaroshevich@gmail.com>
Cr-Commit-Position: refs/heads/master@{#33402}

sdk/objc/api/peerconnection/RTCPeerConnection.h

@@ -285,6 +285,12 @@ RTC_OBJC_EXPORT
     addTransceiverOfType:(RTCRtpMediaType)mediaType
                     init:(RTC_OBJC_TYPE(RTCRtpTransceiverInit) *)init;
 
+/** Tells the PeerConnection that ICE should be restarted. This triggers a need
+ * for negotiation and subsequent offerForConstraints:completionHandler call will act as if
+ * RTCOfferAnswerOptions::ice_restart is true.
+ */
+- (void)restartIce;
+
 /** Generate an SDP offer. */
 - (void)offerForConstraints:(RTC_OBJC_TYPE(RTCMediaConstraints) *)constraints
           completionHandler:(nullable void (^)(RTC_OBJC_TYPE(RTCSessionDescription) * _Nullable sdp,

sdk/objc/api/peerconnection/RTCPeerConnection.mm

@@ -537,6 +537,10 @@ void PeerConnectionDelegateAdapter::OnRemoveTrack(
       nativeRtpTransceiver:nativeTransceiverOrError.MoveValue()];
 }
 
+- (void)restartIce {
+  _peerConnection->RestartIce();
+}
+
 - (void)offerForConstraints:(RTC_OBJC_TYPE(RTCMediaConstraints) *)constraints
           completionHandler:(void (^)(RTC_OBJC_TYPE(RTCSessionDescription) * sessionDescription,
                                       NSError *error))completionHandler {