[RuntimeCallStats] Fix reset scope for tracing

src/counters.h

 // Copyright 2012 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_COUNTERS_H_
 #define V8_COUNTERS_H_
 
 #include "include/v8.h"
 #include "src/allocation.h"
 #include "src/base/platform/elapsed-timer.h"
@@ skipping 785 matching lines @@
 
   RuntimeCallTimer* current_timer() { return current_timer_; }
   bool InUse() { return in_use_; }
 
  private:
   std::stringstream buffer_;
   std::unique_ptr<char[]> buffer_c_str_;
   size_t len_ = 0;
   // Counter to track recursive time events.
   RuntimeCallTimer* current_timer_ = NULL;
+  // Used to track nested tracing scopes.
   bool in_use_;
 };
 
 #define TRACE_RUNTIME_CALL_STATS(isolate, counter_name)                  \
   do {                                                                   \
     if (FLAG_runtime_call_stats) {                                       \
       RuntimeCallStats::CorrectCurrentCounterId(                         \
           isolate->counters()->runtime_call_stats(),                     \
           &RuntimeCallStats::counter_name);                              \
     }                                                                    \
@@ skipping 466 matching lines @@
   // isolate reference and a timer for both.
   Isolate* isolate_for_tracing_ = nullptr;
   RuntimeCallTimer timer_;
   RuntimeCallTimer trace_event_timer_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COUNTERS_H_