Implement standalone event tracing in AppRTCDemo.

webrtc/base/event_tracer.h

 /*
  *  Copyright (c) 2012 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.
  */
 
 // This file defines the interface for event tracing in WebRTC.
 //
 // Event log handlers are set through SetupEventTracer(). User of this API will
 // provide two function pointers to handle event tracing calls.
 //
 // * GetCategoryEnabledPtr
 //   Event tracing system calls this function to determine if a particular
 //   event category is enabled.
 //
 // * AddTraceEventPtr
 //   Adds a tracing event. It is the user's responsibility to log the data
 //   provided.
 //
 // Parameters for the above two functions are described in trace_event.h.
 
 #ifndef WEBRTC_BASE_EVENT_TRACER_H_
 #define WEBRTC_BASE_EVENT_TRACER_H_
 
+#include <stdio.h>
+
 namespace webrtc {
 
 typedef const unsigned char* (*GetCategoryEnabledPtr)(const char* name);
 typedef void (*AddTraceEventPtr)(char phase,
                                  const unsigned char* category_enabled,
                                  const char* name,
                                  unsigned long long id,
                                  int num_args,
                                  const char** arg_names,
                                  const unsigned char* arg_types,
@@ skipping 18 matching lines @@
   static void AddTraceEvent(
       char phase,
       const unsigned char* category_enabled,
       const char* name,
       unsigned long long id,
       int num_args,
       const char** arg_names,
       const unsigned char* arg_types,
       const unsigned long long* arg_values,
       unsigned char flags);
+
+  // Set up internal event tracer.
+  static void SetupInternalTracer();

[tommi, 2015/11/24 16:27:09]

would it make sense to move these out of the class and into a namespace, e.g.
webrtc::internal?
or perhaps rtc::tracing::internal?

+  static bool StartInternalCapture(const char* filename);
+  static void StartInternalCaptureToFile(FILE* file);
+  static void StopInternalCapture();
+  // Make sure we run this, this will tear down the internal tracing.
+  static void ShutdownInternalTracer();
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_BASE_EVENT_TRACER_H_