Compile rtc_api_objc on Mac.

webrtc/api/objc/RTCConfiguration.h

Index: webrtc/api/objc/RTCConfiguration.h
diff --git a/webrtc/api/objc/RTCConfiguration.h b/webrtc/api/objc/RTCConfiguration.h
index 144c8d3bd5ebe041b2309809d684e73db7abf5c3..c9d26946a6d4ab4384e113dc2b88f63e348bc8a7 100644
--- a/webrtc/api/objc/RTCConfiguration.h
+++ b/webrtc/api/objc/RTCConfiguration.h
@@ -53,7 +53,7 @@ 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/*<RTCIceServer *>*/ *iceServers;

[tkchin_webrtc, 2016/02/24 22:39:18]

suggest just having a duplicated line, with a bug prefix so we can search easily
later and edit.

// TODO(<bug>):
// @property(nonatomic, copy) NSArray<RTCIceServer *> *iceServers;

Well actually it looks like you've done this in many places. I don't want to
make you edit all of them so leave as is - but let's add a // TODO(<bug>) at the
top of all the files that this affects.

 
 /** Which candidates the ICE agent is allowed to use. The W3C calls it
  * |iceTransportPolicy|, while in C++ it is called |type|. */
@@ -72,7 +72,7 @@ NS_ASSUME_NONNULL_BEGIN
 /** 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