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

webrtc/sdk/objc/Framework/Classes/RTCConfiguration+Private.h

 /*
  *  Copyright 2015 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 30 matching lines @@
 + (NSString *)stringForRtcpMuxPolicy:(RTCRtcpMuxPolicy)policy;
 
 + (webrtc::PeerConnectionInterface::TcpCandidatePolicy)
     nativeTcpCandidatePolicyForPolicy:(RTCTcpCandidatePolicy)policy;
 
 + (RTCTcpCandidatePolicy)tcpCandidatePolicyForNativePolicy:
     (webrtc::PeerConnectionInterface::TcpCandidatePolicy)nativePolicy;
 
 + (NSString *)stringForTcpCandidatePolicy:(RTCTcpCandidatePolicy)policy;
 
++ (webrtc::PeerConnectionInterface::CandidateNetworkPolicy)
+    nativeCandidateNetworkPolicyForPolicy:(RTCCandidateNetworkPolicy)policy;
+
++ (RTCCandidateNetworkPolicy)candidateNetworkPolicyForNativePolicy:
+    (webrtc::PeerConnectionInterface::CandidateNetworkPolicy)nativePolicy;
+
++ (NSString *)stringForCandidateNetworkPolicy:(RTCCandidateNetworkPolicy)policy;
+
 /**
  * RTCConfiguration struct representation of this RTCConfiguration. This is
  * needed to pass to the underlying C++ APIs.
  */
 - (webrtc::PeerConnectionInterface::RTCConfiguration *)
     createNativeConfiguration;
 
 @end
 
 NS_ASSUME_NONNULL_END