Expose TurnCustomizer as a native ObjC property.

Bug: webrtc:8471
Change-Id: Ic0d904b0c3742e552f20fbebb26d55d2bdd76c72
Reviewed-on: https://webrtc-review.googlesource.com/16566
Commit-Queue: Zeke Chin <tkchin@webrtc.org>
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20481}
diff --git a/sdk/objc/Framework/Classes/PeerConnection/RTCConfiguration.mm b/sdk/objc/Framework/Classes/PeerConnection/RTCConfiguration.mm
index 17aed85..faf34d6 100644
--- a/sdk/objc/Framework/Classes/PeerConnection/RTCConfiguration.mm
+++ b/sdk/objc/Framework/Classes/PeerConnection/RTCConfiguration.mm
@@ -12,6 +12,7 @@
 
 #include <memory>
 
+#import "RTCConfiguration+Native.h"
 #import "RTCIceServer+Private.h"
 #import "RTCIntervalRange+Private.h"
 #import "WebRTC/RTCLogging.h"
@@ -41,6 +42,7 @@
     _shouldPresumeWritableWhenFullyRelayed;
 @synthesize iceCheckMinInterval = _iceCheckMinInterval;
 @synthesize iceRegatherIntervalRange = _iceRegatherIntervalRange;
+@synthesize turnCustomizer = _turnCustomizer;
 
 - (instancetype)init {
   // Copy defaults.
@@ -92,6 +94,7 @@
       _iceRegatherIntervalRange =
           [[RTCIntervalRange alloc] initWithNativeIntervalRange:nativeIntervalRange];
     }
+    _turnCustomizer = config.turn_customizer;
   }
   return self;
 }
@@ -178,6 +181,9 @@
     nativeConfig->ice_regather_interval_range =
         rtc::Optional<rtc::IntervalRange>(*nativeIntervalRange);
   }
+  if (_turnCustomizer) {
+    nativeConfig->turn_customizer = _turnCustomizer;
+  }
   return nativeConfig.release();
 }