Add flag in ios to support disabling high-cost networks.

webrtc/sdk/objc/Framework/Headers/WebRTC/RTCConfiguration.h

Index: webrtc/sdk/objc/Framework/Headers/WebRTC/RTCConfiguration.h
diff --git a/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCConfiguration.h b/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCConfiguration.h
index e8d80e2a7882ee1278f4a50026cf0e5a6d3f2847..5ebcb73dc036cac9a20df205ff80be417dda736c 100644
--- a/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCConfiguration.h
+++ b/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCConfiguration.h
@@ -44,6 +44,12 @@ typedef NS_ENUM(NSInteger, RTCTcpCandidatePolicy) {
   RTCTcpCandidatePolicyDisabled
 };
 
+/** Represents the candidate network policy. */
+typedef NS_ENUM(NSInteger, RTCCandidateNetworkPolicy) {
+  RTCCandidateNetworkPolicyAll,
+  RTCCandidateNetworkPolicyLowCost
+};
+
 /** Represents the continual gathering policy. */
 typedef NS_ENUM(NSInteger, RTCContinualGatheringPolicy) {
   RTCContinualGatheringPolicyGatherOnce,
@@ -74,6 +80,7 @@ RTC_EXPORT
 /** The rtcp-mux policy to use when gathering ICE candidates. */
 @property(nonatomic, assign) RTCRtcpMuxPolicy rtcpMuxPolicy;
 @property(nonatomic, assign) RTCTcpCandidatePolicy tcpCandidatePolicy;
+@property(nonatomic, assign) RTCCandidateNetworkPolicy candidateNetworkPolicy;
 @property(nonatomic, assign)
     RTCContinualGatheringPolicy continualGatheringPolicy;
 @property(nonatomic, assign) int audioJitterBufferMaxPackets;