Support building WebRTC without audio and video for IOS

webrtc/sdk/objc/Framework/Classes/PeerConnection/RTCPeerConnection+Media.mm

+/*
+ *  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 "RTCMediaStream+Private.h"
+#import "RTCPeerConnection+Private.h"
+
+namespace webrtc {
+

[tkchin_webrtc, 2017/06/20 21:51:23]

why does this need to be in its own file?

this file is also supposed to implement the Media category, but it's only used
to implement C++ methods?

+void PeerConnectionDelegateAdapter::OnAddStream(rtc::scoped_refptr<MediaStreamInterface> stream) {
+#if defined(HAVE_RTC_AUDIO) || defined(HAVE_RTC_VIDEO)
+  RTCMediaStream* mediaStream = [[RTCMediaStream alloc] initWithNativeMediaStream:stream];
+  RTCPeerConnection* peer_connection = peer_connection_;
+  [peer_connection.delegate peerConnection:peer_connection didAddStream:mediaStream];
+#endif
+}
+
+void PeerConnectionDelegateAdapter::OnRemoveStream(
+    rtc::scoped_refptr<MediaStreamInterface> stream) {
+#if defined(HAVE_RTC_AUDIO) || defined(HAVE_RTC_VIDEO)
+  RTCMediaStream* mediaStream = [[RTCMediaStream alloc] initWithNativeMediaStream:stream];
+  RTCPeerConnection* peer_connection = peer_connection_;
+  [peer_connection.delegate peerConnection:peer_connection didRemoveStream:mediaStream];
+#endif
+}
+
+}  // namespace webrtc