[counter] reducing the overhead of RuntimeCallTimerScope

src/vm-state-inl.h

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_VM_STATE_INL_H_
 #define V8_VM_STATE_INL_H_
 
 #include "src/vm-state.h"
 #include "src/log.h"
 #include "src/simulator.h"
@@ skipping 40 matching lines @@
 VMState<Tag>::~VMState() {
   if (FLAG_log_timer_events && previous_tag_ != EXTERNAL && Tag == EXTERNAL) {
     LOG(isolate_, TimerEvent(Logger::END, TimerEventExternal::name()));
   }
   isolate_->set_current_vm_state(previous_tag_);
 }
 
 ExternalCallbackScope::ExternalCallbackScope(Isolate* isolate, Address callback)
     : isolate_(isolate),
       callback_(callback),
-      previous_scope_(isolate->external_callback_scope()),
-      timer_(&isolate->counters()->runtime_call_stats()->ExternalCallback,
-             isolate->counters()->runtime_call_stats()->current_timer()) {
+      previous_scope_(isolate->external_callback_scope()) {
 #ifdef USE_SIMULATOR
   scope_address_ = Simulator::current(isolate)->get_sp();
 #endif
   isolate_->set_external_callback_scope(this);
   if (FLAG_runtime_call_stats) {
-    isolate_->counters()->runtime_call_stats()->Enter(&timer_);
+    RuntimeCallStats* stats = isolate->counters()->runtime_call_stats();
+    timer_.Initialize(&stats->ExternalCallback, stats->current_timer());
+    stats->Enter(&timer_);
   }
 }
 
 ExternalCallbackScope::~ExternalCallbackScope() {
   if (FLAG_runtime_call_stats) {
     isolate_->counters()->runtime_call_stats()->Leave(&timer_);
   }
   isolate_->set_external_callback_scope(previous_scope_);
 }
 
 Address ExternalCallbackScope::scope_address() {
 #ifdef USE_SIMULATOR
   return scope_address_;
 #else
   return reinterpret_cast<Address>(this);
 #endif
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_VM_STATE_INL_H_