Update API for Objective-C RTCPeerConnection.

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.
+ */
+
+#import "RTCPeerConnection.h"
+
+#include "talk/app/webrtc/peerconnectioninterface.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface RTCPeerConnection ()
+
+/** The native PeerConnectionInterface created during construction. */
+@property(nonatomic, readonly)
+    rtc::scoped_refptr<webrtc::PeerConnectionInterface> nativePeerConnection;
+
++ (webrtc::PeerConnectionInterface::SignalingState)nativeSignalingStateForState:
+    (RTCSignalingState)state;
+
++ (RTCSignalingState)signalingStateForNativeState:
+    (webrtc::PeerConnectionInterface::SignalingState)nativeState;
+
++ (NSString *)stringForSignalingState:(RTCSignalingState)state;
+
++ (webrtc::PeerConnectionInterface::IceConnectionState)
+    nativeIceConnectionStateForState:(RTCIceConnectionState)state;
+
++ (RTCIceConnectionState)iceConnectionStateForNativeState:
+    (webrtc::PeerConnectionInterface::IceConnectionState)nativeState;
+
++ (NSString *)stringForIceConnectionState:(RTCIceConnectionState)state;
+
++ (webrtc::PeerConnectionInterface::IceGatheringState)
+    nativeIceGatheringStateForState:(RTCIceGatheringState)state;
+
++ (RTCIceGatheringState)iceGatheringStateForNativeState:
+    (webrtc::PeerConnectionInterface::IceGatheringState)nativeState;
+
++ (NSString *)stringForIceGatheringState:(RTCIceGatheringState)state;
+
++ (webrtc::PeerConnectionInterface::StatsOutputLevel)
+    nativeStatsOutputLevelForLevel:(RTCStatsOutputLevel)level;
+
+@end
+
+NS_ASSUME_NONNULL_END