Use high precision timestamp for Event.timestamp

third_party/WebKit/Source/core/timing/PerformanceBase.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2012 Intel Inc. 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.
@@ skipping 397 matching lines @@
     copyToVector(m_activeObservers, observers);
     m_activeObservers.clear();
     for (size_t i = 0; i < observers.size(); ++i) {
         if (observers[i]->shouldBeSuspended())
             m_suspendedObservers.add(observers[i]);
         else
             observers[i]->deliver();
     }
 }
 
+double toSafePrecisionTime(double timeInSeconds)
+{
+    static const double precision = 0.000005; // in seconds
+    return floor(timeInSeconds / precision) * precision;
+}
+
 double PerformanceBase::now() const
 {
     double nowSeconds = monotonicallyIncreasingTime() - m_timeOrigin;
-    const double resolutionSeconds = 0.000005;
-    return 1000.0 * floor(nowSeconds / resolutionSeconds) * resolutionSeconds;
+    return 1000.0 * toSafePrecisionTime(nowSeconds);
 }
 
 DEFINE_TRACE(PerformanceBase)
 {
     visitor->trace(m_frameTimingBuffer);
     visitor->trace(m_resourceTimingBuffer);
     visitor->trace(m_userTiming);
     visitor->trace(m_observers);
     visitor->trace(m_activeObservers);
     visitor->trace(m_suspendedObservers);
     RefCountedGarbageCollectedEventTargetWithInlineData<PerformanceBase>::trace(visitor);
 }
 
 } // namespace blink