Compile rtc_api_objc on Mac.

webrtc/api/objc/RTCConfiguration.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.
  */
 
 #import <Foundation/Foundation.h>
 
 @class RTCIceServer;
 
+// TODO(hjon): Update nullability types. See http://crbug/webrtc/5592
+
 /**
  * Represents the ice transport policy. This exposes the same states in C++,
  * which include one more state than what exists in the W3C spec.
  */
 typedef NS_ENUM(NSInteger, RTCIceTransportPolicy) {
   RTCIceTransportPolicyNone,
   RTCIceTransportPolicyRelay,
   RTCIceTransportPolicyNoHost,
   RTCIceTransportPolicyAll
 };
@@ skipping 21 matching lines @@
 typedef NS_ENUM(NSInteger, RTCEncryptionKeyType) {
   RTCEncryptionKeyTypeRSA,
   RTCEncryptionKeyTypeECDSA,
 };
 
 NS_ASSUME_NONNULL_BEGIN
 
 @interface RTCConfiguration : NSObject
 
 /** An array of Ice Servers available to be used by ICE. */
-@property(nonatomic, copy) NSArray<RTCIceServer *> *iceServers;
+@property(nonatomic, copy, nonnull) NSArray *iceServers;
+// @property(nonatomic, copy) NSArray<RTCIceServer *> *iceServers;
 
 /** Which candidates the ICE agent is allowed to use. The W3C calls it
  * |iceTransportPolicy|, while in C++ it is called |type|. */
 @property(nonatomic, assign) RTCIceTransportPolicy iceTransportPolicy;
 
 /** The media-bundling policy to use when gathering ICE candidates. */
 @property(nonatomic, assign) RTCBundlePolicy bundlePolicy;
 
 /** The rtcp-mux policy to use when gathering ICE candidates. */
 @property(nonatomic, assign) RTCRtcpMuxPolicy rtcpMuxPolicy;
 @property(nonatomic, assign) RTCTcpCandidatePolicy tcpCandidatePolicy;
 @property(nonatomic, assign) int audioJitterBufferMaxPackets;
 @property(nonatomic, assign) int iceConnectionReceivingTimeout;
 @property(nonatomic, assign) int iceBackupCandidatePairPingInterval;
 
 /** Key type used to generate SSL identity. Default is ECDSA. */
 @property(nonatomic, assign) RTCEncryptionKeyType keyType;
 
-- (instancetype)init NS_DESIGNATED_INITIALIZER;
+- (nonnull instancetype)init NS_DESIGNATED_INITIALIZER;
 
 @end
 
 NS_ASSUME_NONNULL_END