Reland: Add BWE plot to event log analyzer.

webrtc/call/rtc_event_log.h

 /*
  *  Copyright (c) 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.
  */
 
@@ skipping 91 matching lines @@
   // The result is stored in the given EventStream object.
   // The order of the events in the EventStream is implementation defined.
   // The current implementation writes a LOG_START event, then the old
   // configurations, then the remaining events in timestamp order and finally
   // a LOG_END event. However, this might change without further notice.
   // TODO(terelius): Change result type to a vector?
   static bool ParseRtcEventLog(const std::string& file_name,
                                rtclog::EventStream* result);
 };
 
+// No-op implementation is used if flag is not set, or in tests.
+class RtcEventLogNullImpl final : public RtcEventLog {
+ public:
+  bool StartLogging(const std::string& file_name,
+                    int64_t max_size_bytes) override {
+    return false;
+  }
+  bool StartLogging(rtc::PlatformFile platform_file,
+                    int64_t max_size_bytes) override;
+  void StopLogging() override {}
+  void LogVideoReceiveStreamConfig(
+      const VideoReceiveStream::Config& config) override {}
+  void LogVideoSendStreamConfig(
+      const VideoSendStream::Config& config) override {}
+  void LogRtpHeader(PacketDirection direction,
+                    MediaType media_type,
+                    const uint8_t* header,
+                    size_t packet_length) override {}
+  void LogRtcpPacket(PacketDirection direction,
+                     MediaType media_type,
+                     const uint8_t* packet,
+                     size_t length) override {}
+  void LogAudioPlayout(uint32_t ssrc) override {}
+  void LogBwePacketLossEvent(int32_t bitrate,
+                             uint8_t fraction_loss,
+                             int32_t total_packets) override {}
+};
+
 }  // namespace webrtc
 
 #endif  // WEBRTC_CALL_RTC_EVENT_LOG_H_