Build WebRTC with data channel only.

webrtc/logging/rtc_event_log/rtc_event_log_factory.cc

+/*
+ *  Copyright 2017 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.
+ */
+
+#include "webrtc/logging/rtc_event_log/rtc_event_log_factory.h"
+
+#include "webrtc/logging/rtc_event_log/rtc_event_log.h"
+
+namespace webrtc {
+
+std::unique_ptr<RtcEventLog> RtcEventLogFactory::CreateRtcEventLog() {
+  return RtcEventLog::Create();
+}
+
+std::unique_ptr<RtcEventLogFactoryInterface> CreateRtcEventLogFactory() {
+  return std::unique_ptr<RtcEventLogFactoryInterface>(new RtcEventLogFactory());
+}
+
+}  // namespace webrtc