[Tracing] Show background parsing runtime statistics in tracing.

src/parsing/parser.cc

Index: src/parsing/parser.cc
diff --git a/src/parsing/parser.cc b/src/parsing/parser.cc
index 842d3520330f80965b332222072408b5d4f0bdf8..b8c780fc0823cb7f4aad2b85b75581da033fbd66 100644
--- a/src/parsing/parser.cc
+++ b/src/parsing/parser.cc
@@ -3809,8 +3809,6 @@ void Parser::Internalize(Isolate* isolate, Handle<Script> script, bool error) {
           v8::tracing::TracingCategoryObserver::ENABLED_BY_NATIVE) {
     // Copy over the counters from the background thread to the main counters on
     // the isolate.
-    // TODO(cbruni,lpy): properly attach the runtime stats to the trace for
-    // background parsing.
     isolate->counters()->runtime_call_stats()->Add(runtime_call_stats_);
   }
 }
@@ -3873,9 +3871,13 @@ void Parser::ParseOnBackground(ParseInfo* info) {
     if (result != NULL) *info->cached_data() = logger.GetScriptData();
     log_ = NULL;
   }
-  if (FLAG_runtime_stats) {
-    // TODO(cbruni,lpy): properly attach the runtime stats to the trace for
-    // background parsing.
+  if (FLAG_runtime_stats &
+      v8::tracing::TracingCategoryObserver::ENABLED_BY_TRACING) {
+    auto value = v8::tracing::TracedValue::Create();
+    runtime_call_stats_->Dump(value.get());
+    TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("v8.runtime_stats"),
+                         "V8.RuntimeStats", TRACE_EVENT_SCOPE_THREAD,
+                         "runtime-call-stats", std::move(value));
   }
 }