[Tracing] Fix inaccurate timer calculation in runtime statistics.

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 503 matching lines @@
     timer_.Stop();
     counter_->count++;
     counter_->time += delta;
     if (parent_ != NULL) {
       // Adjust parent timer so that it does not include sub timer's time.
       parent_->counter_->time -= delta;
     }
     return parent_;
   }
 
+  inline void Elapsed() {
+    base::TimeDelta delta = timer_.Elapsed();
+    counter_->time += delta;
+    if (parent_ != nullptr) {
+      parent_->counter_->time -= delta;
+      parent_->Elapsed();
+    }
+    timer_.Restart();
+  }
+
   RuntimeCallCounter* counter_ = nullptr;
   RuntimeCallTimer* parent_ = nullptr;
   base::ElapsedTimer timer_;
 };
 
 #define FOR_EACH_API_COUNTER(V)                            \
   V(ArrayBuffer_Cast)                                      \
   V(ArrayBuffer_Neuter)                                    \
   V(ArrayBuffer_New)                                       \
   V(Array_CloneElementAt)                                  \
@@ skipping 740 matching lines @@
   }
 
   Isolate* isolate_ = nullptr;
   RuntimeCallTimer timer_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COUNTERS_H_