[Tracing] Use TracingCategoryObserver in runtime statistics

src/tracing/tracing-category-observer.cc

Index: src/tracing/tracing-category-observer.cc
diff --git a/src/tracing/tracing-category-observer.cc b/src/tracing/tracing-category-observer.cc
index 9a318bd699a8082121541a0560fc39992572d852..710488a1c300e135cdef661a6ce0949bac8d4928 100644
--- a/src/tracing/tracing-category-observer.cc
+++ b/src/tracing/tracing-category-observer.cc
@@ -17,6 +17,7 @@ void TracingCategoryObserver::SetUp() {
   TracingCategoryObserver::instance_ = new TracingCategoryObserver();
   v8::internal::V8::GetCurrentPlatform()->AddTraceStateObserver(
       TracingCategoryObserver::instance_);
+  TRACE_EVENT_WARMUP_CATEGORY(TRACE_DISABLED_BY_DEFAULT("v8.runtime_stats"));
 }
 
 void TracingCategoryObserver::TearDown() {