Add Chromium-style TimeDelta, Time and TimeTicks classes, and a new ElapsedTimer class.

src/counters.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 227 matching lines @@
 
 // A HistogramTimer allows distributions of results to be created.
 class HistogramTimer : public Histogram {
  public:
   HistogramTimer() { }
   HistogramTimer(const char* name,
                  int min,
                  int max,
                  int num_buckets,
                  Isolate* isolate)
-      : Histogram(name, min, max, num_buckets, isolate),
-        start_time_(0),
-        stop_time_(0) { }
+      : Histogram(name, min, max, num_buckets, isolate) {}
 
   // Start the timer.
   void Start();
 
   // Stop the timer and record the results.
   void Stop();
 
   // Returns true if the timer is running.
   bool Running() {
-    return Enabled() && (start_time_ != 0) && (stop_time_ == 0);
+    return Enabled() && timer_.IsStarted();
   }
 
  private:
-  int64_t start_time_;
-  int64_t stop_time_;
+  ElapsedTimer timer_;
 };
 
 // Helper class for scoping a HistogramTimer.
 class HistogramTimerScope BASE_EMBEDDED {
  public:
   explicit HistogramTimerScope(HistogramTimer* timer) :
   timer_(timer) {
     timer_->Start();
   }
   ~HistogramTimerScope() {
     timer_->Stop();
   }
  private:
   HistogramTimer* timer_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_COUNTERS_H_