Implement a new flow event API that allows binding flow events and regular events.

ui/gl/angle_platform_impl.cc

Index: ui/gl/angle_platform_impl.cc
diff --git a/ui/gl/angle_platform_impl.cc b/ui/gl/angle_platform_impl.cc
index a405f8e0859e1d577b9b18108b8aae5ea1523ac5..57e5a350fce19e87b8e02297c2bf577b36a21884 100644
--- a/ui/gl/angle_platform_impl.cc
+++ b/ui/gl/angle_platform_impl.cc
@@ -44,9 +44,19 @@ angle::Platform::TraceEventHandle ANGLEPlatformImpl::addTraceEvent(
       base::TraceTicks() + base::TimeDelta::FromSecondsD(timestamp);
   base::trace_event::TraceEventHandle handle =
       TRACE_EVENT_API_ADD_TRACE_EVENT_WITH_THREAD_ID_AND_TIMESTAMP(
-          phase, category_group_enabled, name, id, trace_event_internal::kNoId,
-          base::PlatformThread::CurrentId(), timestamp_tt, num_args, arg_names,
-          arg_types, arg_values, nullptr, flags);
+          phase,
+          category_group_enabled,
+          name,
+          id,
+          trace_event_internal::kNoId,  // context_id
+          base::PlatformThread::CurrentId(),

[beaudoin, 2015/07/29 18:55:43]

Ditto.

+          timestamp_tt,
+          num_args,
+          arg_names,
+          arg_types,
+          arg_values,
+          NULL,
+          flags);
   angle::Platform::TraceEventHandle result;
   memcpy(&result, &handle, sizeof(result));
   return result;