Expose enableDscp in Obj-C API.

network_priority was already exposed, but without the ability to set
enable_dscp, it wasn't actually doing anything.

Bug: webrtc:5658
Change-Id: I092bc3dd46e3e7be363313203428bccfccccf3c5
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/171641
Reviewed-by: Anders Carlsson <andersc@webrtc.org>
Commit-Queue: Taylor <deadbeef@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30951}
diff --git a/sdk/objc/api/peerconnection/RTCConfiguration.h b/sdk/objc/api/peerconnection/RTCConfiguration.h
index 7400296..44d0922 100644
--- a/sdk/objc/api/peerconnection/RTCConfiguration.h
+++ b/sdk/objc/api/peerconnection/RTCConfiguration.h
@@ -72,6 +72,11 @@
 RTC_OBJC_EXPORT
 @interface RTCConfiguration : NSObject
 
+/** If true, allows DSCP codes to be set on outgoing packets, configured using
+ *  networkPriority field of RTCRtpEncodingParameters. Defaults to false.
+ */
+@property(nonatomic, assign) BOOL enableDscp;
+
 /** An array of Ice Servers available to be used by ICE. */
 @property(nonatomic, copy) NSArray<RTCIceServer *> *iceServers;