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 a98c71b75e24fe5987d5b88e86d2b11afb7cd413..ae25310c1247b98f130d4f6a01ae71e0a9a62202 100644
--- a/webrtc/logging/rtc_event_log/rtc_event_log.h
+++ b/webrtc/logging/rtc_event_log/rtc_event_log.h
@@ -169,7 +169,13 @@ class RtcEventLogNullImpl final : 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 VideoReceiveStream::Config& config) override {}