tp: fix args for json instant events

Bug: https://github.com/google/perfetto/issues/520
Fixes: https://github.com/google/perfetto/issues/520
Change-Id: I1275d2498e17b43710e61db7a56e5471e88bbf82
diff --git a/src/trace_processor/importers/json/json_trace_parser.cc b/src/trace_processor/importers/json/json_trace_parser.cc
index b087963..536041d 100644
--- a/src/trace_processor/importers/json/json_trace_parser.cc
+++ b/src/trace_processor/importers/json/json_trace_parser.cc
@@ -184,8 +184,8 @@
         // We don't handle tts here as we do in the 'E'
         // case above as it's not well defined for aysnc slices.
       } else {
-        context_->slice_tracker->Scoped(timestamp, track_id, cat_id, name_id,
-                                        0);
+        context_->slice_tracker->Scoped(timestamp, track_id, cat_id, name_id, 0,
+                                        args_inserter);
         MaybeAddFlow(track_id, value);
       }
       break;