Use high precision timestamp for Event.timestamp

third_party/WebKit/Source/core/dom/DOMHighResTimeStamp.h

+// Copyright 2015 The Chromium 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 DOMHighResTimeStamp_h
+#define DOMHighResTimeStamp_h
+
+namespace blink {
+
+typedef double DOMHighResTimeStamp;
+
+inline DOMHighResTimeStamp convertSecondsToDOMHighResTimeStamp(double seconds)
+{
+    return static_cast<DOMHighResTimeStamp>(seconds * 1000.0);
+}
+
+inline double convertDOMHighResTimeStampToSeconds(DOMHighResTimeStamp milliseconds)
+{
+    return milliseconds / 1000.0;
+}
+
+} // namespace blink
+
+#endif // DOMHighResTimeStamp_h