Build WebRTC with data channel only.

webrtc/pc/peerconnection.cc

Index: webrtc/pc/peerconnection.cc
diff --git a/webrtc/pc/peerconnection.cc b/webrtc/pc/peerconnection.cc
index a3981039e6cfe89554092b4c14d7f2f7b0f175e4..3810a423ad68b6fdd5a8590ac6f29c3ef8da1f47 100644
--- a/webrtc/pc/peerconnection.cc
+++ b/webrtc/pc/peerconnection.cc
@@ -398,10 +398,15 @@ PeerConnection::PeerConnection(PeerConnectionFactory* factory)
       signaling_state_(kStable),
       ice_connection_state_(kIceConnectionNew),
       ice_gathering_state_(kIceGatheringNew),
+#ifdef HAVE_MEDIA
       event_log_(RtcEventLog::Create()),
+#else
+      event_log_(std::unique_ptr<RtcEventLog>(new RtcEventLogNullImpl())),
+#endif
       rtcp_cname_(GenerateRtcpCname()),
       local_streams_(StreamCollection::Create()),
-      remote_streams_(StreamCollection::Create()) {}
+      remote_streams_(StreamCollection::Create()) {
+}
 
 PeerConnection::~PeerConnection() {
   TRACE_EVENT0("webrtc", "PeerConnection::~PeerConnection");