Introduce RtcEvent and subclasses

webrtc/logging/rtc_event_log/events/rtc_event.h

+/*
+ *  Copyright (c) 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.
+ */
+
+#ifndef WEBRTC_LOGGING_RTC_EVENT_LOG_EVENTS_RTC_EVENT_H_
+#define WEBRTC_LOGGING_RTC_EVENT_LOG_EVENTS_RTC_EVENT_H_
+
+namespace webrtc {
+
+// This class allows us to store unencoded RTC events. Subclasses of this class
+// store the actual information. This allows us to keep all unencoded events,
+// even when their type and associated information differ, in the same buffer.
+// Additionally, it prevents dependency leaking - a module that only logs
+// events of type RtcEvent_A doesn't need to know about anything associated
+// with events of type RtcEvent_B.
+class RtcEvent {
+ public:
+  // Subclasses of this class have to associate themselves with a unique
+  // of Type. This leaks the information of existing subclasses into the

[terelius, 2017/09/11 09:42:32]

"unique of Type"?

[eladalon, 2017/09/11 15:44:12]

Unique value. Thank for catching.

+  // superclass, but the *actual* information - rtclog::StreamConfig, etc. -
+  // is kept separate.
+  enum class Type {

[terelius, 2017/09/11 09:42:31]

I'd prefer to not order these alphabetically, but by "topic". I.e. keep all
StreamConfigs together. 

[eladalon, 2017/09/11 15:44:12]

If we don't sort alphabetically, these values (and their corresponding classes
and functions in the CLs on top of this one) will be sorted differently than the
#include lines, lines in BUILD.gn, etc. I think that would be confusing.
Please also note that I've named some entries to keep things bunched together
"correctly" even after it was alphabetically sorted.

+    AudioNetworkAdaptation,
+    AudioPlayout,
+    AudioReceiveStreamConfig,
+    AudioSendStreamConfig,
+    BweUpdateDelayBased,
+    BweUpdateLossBased,
+    LoggingStarted,
+    LoggingStopped,
+    ProbeClusterCreated,
+    ProbeResultFailure,
+    ProbeResultSuccess,
+    RtcpHeaderIncoming,
+    RtcpHeaderOutgoing,
+    RtpHeaderIncoming,
+    RtpHeaderOutgoing,
+    VideoReceiveStreamConfig,
+    VideoSendStreamConfig
+  };
+
+  virtual ~RtcEvent() = default;
+
+  virtual Type GetType() const = 0;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_LOGGING_RTC_EVENT_LOG_EVENTS_RTC_EVENT_H_