Trace tracing Start/Stop events.

webrtc/base/event_tracer.cc

Index: webrtc/base/event_tracer.cc
diff --git a/webrtc/base/event_tracer.cc b/webrtc/base/event_tracer.cc
index 4174589d366a48cf4d20d7cc1bceb8fc0eb3ca4f..97be53c45cb7751629808554c69d0062d592af6e 100644
--- a/webrtc/base/event_tracer.cc
+++ b/webrtc/base/event_tracer.cc
@@ -158,9 +158,11 @@ class EventLogger final {
 
     // Finally start, everything should be set up now.
     logging_thread_.Start();
+    TRACE_EVENT_INSTANT0("webrtc", "EventLogger::Start");

[tommi, 2016/02/29 13:12:27]

would TRACE_EVENT_BEGIN0 and TRACE_EVENT_END0 be more appropriate?

Also, Start() and Stop() must occur on the same thread then but I don't see any
thread checks.

[pbos-webrtc, 2016/02/29 13:23:43]

I don't think it's particularly useful to have a begin/end event that spans the
entire tracing period (it'd just add one bar that spans the entire graph). Added
thread checks.

   }
 
   void Stop() {
+    TRACE_EVENT_INSTANT0("webrtc", "EventLogger::Stop");
     // Try to stop. Abort if we're not currently logging.
     if (rtc::AtomicOps::CompareAndSwap(&g_event_logging_active, 1, 0) == 0)
       return;