Build WebRTC with data channel only.

webrtc/logging/rtc_event_log/rtc_event_log.h

Index: webrtc/logging/rtc_event_log/rtc_event_log.h
diff --git a/webrtc/logging/rtc_event_log/rtc_event_log.h b/webrtc/logging/rtc_event_log/rtc_event_log.h
index bb4cc2e781fbfc89719cfbebed96e9b739f13eda..f23beaa9e048a985c075c8e823fbff1be36d951e 100644
--- a/webrtc/logging/rtc_event_log/rtc_event_log.h
+++ b/webrtc/logging/rtc_event_log/rtc_event_log.h
@@ -15,6 +15,7 @@
 #include <string>
 #include <vector>
 
+#include "webrtc/base/logging.h"
 #include "webrtc/base/platform_file.h"
 #include "webrtc/config.h"
 
@@ -189,7 +190,13 @@ class RtcEventLogNullImpl : public RtcEventLog {
     return false;
   }
   bool StartLogging(rtc::PlatformFile platform_file,
-                    int64_t max_size_bytes) override;
+                    int64_t max_size_bytes) override {
+    // The platform_file is open and needs to be closed.
+    if (!rtc::ClosePlatformFile(platform_file)) {
+      LOG(LS_ERROR) << "Can't close file.";
+    }
+    return false;
+  }
   void StopLogging() override {}
   void LogVideoReceiveStreamConfig(
       const rtclog::StreamConfig& config) override {}