Adding API for "presume writable when fully relayed" ICE option.

webrtc/sdk/objc/Framework/Classes/RTCConfiguration.mm

Index: webrtc/sdk/objc/Framework/Classes/RTCConfiguration.mm
diff --git a/webrtc/sdk/objc/Framework/Classes/RTCConfiguration.mm b/webrtc/sdk/objc/Framework/Classes/RTCConfiguration.mm
index b315e5073fa3528d2d7f0c8030fd6697f39ab929..2a11f2d316a74f4ad43b4b1cdd9e5467bb517977 100644
--- a/webrtc/sdk/objc/Framework/Classes/RTCConfiguration.mm
+++ b/webrtc/sdk/objc/Framework/Classes/RTCConfiguration.mm
@@ -33,6 +33,7 @@
     _iceBackupCandidatePairPingInterval;
 @synthesize keyType = _keyType;
 @synthesize iceCandidatePoolSize = _iceCandidatePoolSize;
+@synthesize presumeWritableWhenFullyRelayed = _presumeWritableWhenFullyRelayed;
 
 - (instancetype)init {
   if (self = [super init]) {
@@ -59,13 +60,15 @@
         config.ice_backup_candidate_pair_ping_interval;
     _keyType = RTCEncryptionKeyTypeECDSA;
     _iceCandidatePoolSize = config.ice_candidate_pool_size;
+    _presumeWritableWhenFullyRelayed =
+        config.presume_writable_when_fully_relayed;
   }
   return self;
 }
 
 - (NSString *)description {
   return [NSString stringWithFormat:
-      @"RTCConfiguration: {\n%@\n%@\n%@\n%@\n%@\n%@\n%@\n%d\n%d\n%d\n%d\n}\n",
+      @"RTCConfiguration: {\n%@\n%@\n%@\n%@\n%@\n%@\n%@\n%d\n%d\n%d\n%d\n%d\n}\n",
       _iceServers,
       [[self class] stringForTransportPolicy:_iceTransportPolicy],
       [[self class] stringForBundlePolicy:_bundlePolicy],
@@ -77,7 +80,8 @@
       _audioJitterBufferMaxPackets,
       _iceConnectionReceivingTimeout,
       _iceBackupCandidatePairPingInterval,
-      _iceCandidatePoolSize];
+      _iceCandidatePoolSize,
+      _presumeWritableWhenFullyRelayed];
 }
 
 #pragma mark - Private
@@ -121,6 +125,8 @@
     nativeConfig->certificates.push_back(certificate);
   }
   nativeConfig->ice_candidate_pool_size = _iceCandidatePoolSize;
+  nativeConfig->presume_writable_when_fully_relayed =
+      _presumeWritableWhenFullyRelayed;
 
   return nativeConfig.release();
 }