[runtime] Minimize runtime call stats overhead when it is disabled.

src/counters.cc

Index: src/counters.cc
diff --git a/src/counters.cc b/src/counters.cc
index 4f5c251a0cce8a42f5f33e057c4032f493b365cc..3b67c48e94bc83c3b4a2c6fc1f4c112ee82273ea 100644
--- a/src/counters.cc
+++ b/src/counters.cc
@@ -272,25 +272,20 @@ void RuntimeCallCounter::Reset() {
   time = base::TimeDelta();
 }
 
-void RuntimeCallStats::Enter(RuntimeCallCounter* counter) {
-  RuntimeCallTimer* timer = new RuntimeCallTimer();
-  timer->Initialize(counter, current_timer_);
-  Enter(timer);
-}
-
-void RuntimeCallStats::Enter(RuntimeCallTimer* timer_) {
-  current_timer_ = timer_;
-  current_timer_->Start();
-}
-
-void RuntimeCallStats::Leave() {
-  RuntimeCallTimer* timer = current_timer_;
-  Leave(timer);
-  delete timer;
+// static
+void RuntimeCallStats::Enter(Isolate* isolate, RuntimeCallTimer* timer,
+                             CounterId counter_id) {
+  RuntimeCallStats* stats = isolate->counters()->runtime_call_stats();
+  RuntimeCallCounter* counter = &(stats->*counter_id);
+  timer->Start(counter, stats->current_timer_);
+  stats->current_timer_ = timer;
 }
 
-void RuntimeCallStats::Leave(RuntimeCallTimer* timer) {
-  current_timer_ = timer->Stop();
+// static
+void RuntimeCallStats::Leave(Isolate* isolate, RuntimeCallTimer* timer) {
+  RuntimeCallStats* stats = isolate->counters()->runtime_call_stats();
+  DCHECK_EQ(stats->current_timer_, timer);
+  stats->current_timer_ = timer->Stop();
 }
 
 void RuntimeCallStats::Print(std::ostream& os) {
@@ -324,17 +319,5 @@ void RuntimeCallStats::Reset() {
   this->UnexpectedStubMiss.Reset();
 }
 
-void RuntimeCallTimerScope::Enter(Isolate* isolate,
-                                  RuntimeCallCounter* counter) {
-  isolate_ = isolate;
-  RuntimeCallStats* stats = isolate->counters()->runtime_call_stats();
-  timer_.Initialize(counter, stats->current_timer());
-  stats->Enter(&timer_);
-}
-
-void RuntimeCallTimerScope::Leave() {
-  isolate_->counters()->runtime_call_stats()->Leave(&timer_);
-}
-
 }  // namespace internal
 }  // namespace v8