Add support for TraceEvent before the native library is loaded.

base/debug/trace_event_impl.h

Index: base/debug/trace_event_impl.h
diff --git a/base/debug/trace_event_impl.h b/base/debug/trace_event_impl.h
index 1b1fce34cc209b452da54cad9b68f10696f4b79e..94016841d45a6e5937bd50b980f1857d050b567c 100644
--- a/base/debug/trace_event_impl.h
+++ b/base/debug/trace_event_impl.h
@@ -544,6 +544,17 @@ class BASE_EXPORT TraceLog {
   void Flush(const OutputCallback& cb);
   void FlushButLeaveBufferIntact(const OutputCallback& flush_output_callback);
 
+  // Can be called by clients to add custom events to the trace log without
+  // using the TRACE_EVENT* macros. This must only be called when category group
+  // is enabled for recording.
+  TraceEventHandle AddCustomTraceEvent(

[dsinclair, 2015/01/27 14:43:30]

Instead of AddCustomTraceEvent, I think we should either update
AddTraceEventWithThreadIdAndTimestamp to also take the thread_now or add a
variant of that method that takes thread_now. 

[Benoit L, 2015/02/09 16:34:01]

Done.

+      char phase,
+      const unsigned char* category_group_enabled,
+      const char* name,
+      int thread_id,
+      const TimeTicks& timestamp,
+      const TimeTicks& thread_time);
+
   // Called by TRACE_EVENT* macros, don't call this directly.
   // The name parameter is a category group for example:
   // TRACE_EVENT0("renderer,webkit", "WebViewImpl::HandleInputEvent")
@@ -699,6 +710,21 @@ class BASE_EXPORT TraceLog {
                                     const TimeTicks& timestamp,
                                     TraceEvent* trace_event);
 
+  TraceEventHandle AddTraceEventInternal(
+      char phase,
+      const unsigned char* category_group_enabled,
+      const char* name,
+      unsigned long long id,
+      int thread_id,
+      const TimeTicks& timestamp,
+      const TimeTicks& thread_time,
+      int num_args,
+      const char** arg_names,
+      const unsigned char* arg_types,
+      const unsigned long long* arg_values,
+      const scoped_refptr<ConvertableToTraceFormat>* convertable_values,
+      unsigned char flags);
+
   TraceEvent* AddEventToThreadSharedChunkWhileLocked(TraceEventHandle* handle,
                                                      bool check_buffer_is_full);
   void CheckIfBufferIsFullWhileLocked();