Refactor some ObjC API init methods.

webrtc/api/objc/RTCPeerConnection+Private.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.
  */
 
@@ skipping 40 matching lines @@
 
 } // namespace webrtc
 
 
 @interface RTCPeerConnection ()
 
 /** The native PeerConnectionInterface created during construction. */
 @property(nonatomic, readonly)
     rtc::scoped_refptr<webrtc::PeerConnectionInterface> nativePeerConnection;
 
+/** Initialize an RTCPeerConnection with a configuration, constraints, and
+ *  delegate.
+ */
+- (instancetype)initWithFactory:
+    (RTCPeerConnectionFactory *)factory
+                  configuration:
+    (RTCConfiguration *)configuration
+                    constraints:
+    (RTCMediaConstraints *)constraints
+                       delegate:
+    (nullable id<RTCPeerConnectionDelegate>)delegate
+    NS_DESIGNATED_INITIALIZER;
+
 + (webrtc::PeerConnectionInterface::SignalingState)nativeSignalingStateForState:
     (RTCSignalingState)state;
 
 + (RTCSignalingState)signalingStateForNativeState:
     (webrtc::PeerConnectionInterface::SignalingState)nativeState;
 
 + (NSString *)stringForSignalingState:(RTCSignalingState)state;
 
 + (webrtc::PeerConnectionInterface::IceConnectionState)
     nativeIceConnectionStateForState:(RTCIceConnectionState)state;
@@ skipping 10 matching lines @@
     (webrtc::PeerConnectionInterface::IceGatheringState)nativeState;
 
 + (NSString *)stringForIceGatheringState:(RTCIceGatheringState)state;
 
 + (webrtc::PeerConnectionInterface::StatsOutputLevel)
     nativeStatsOutputLevelForLevel:(RTCStatsOutputLevel)level;
 
 @end
 
 NS_ASSUME_NONNULL_END