Allow binding point to be specified on flow end events.

base/trace_event/trace_event_impl.cc

Index: base/trace_event/trace_event_impl.cc
diff --git a/base/trace_event/trace_event_impl.cc b/base/trace_event/trace_event_impl.cc
index 3d58d873ad52552cf7473e04c3bf505b7bb9cee2..c9b0d274af5377462d6b54de5e7258e0862ab64f 100644
--- a/base/trace_event/trace_event_impl.cc
+++ b/base/trace_event/trace_event_impl.cc
@@ -753,6 +753,9 @@ void TraceEvent::AppendAsJSON(
   if (flags_ & TRACE_EVENT_FLAG_HAS_ID)
     StringAppendF(out, ",\"id\":\"0x%" PRIx64 "\"", static_cast<uint64>(id_));
 
+  if (flags_ & TRACE_EVENT_FLAG_BIND_TO_ENCLOSING)
+    StringAppendF(out, ",\"bp\":\"e\"");
+
   // Instant events also output their scope.
   if (phase_ == TRACE_EVENT_PHASE_INSTANT) {
     char scope = '?';