Use high precision timestamp for Event.timestamp

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

Index: third_party/WebKit/Source/core/timing/PerformanceBase.h
diff --git a/third_party/WebKit/Source/core/timing/PerformanceBase.h b/third_party/WebKit/Source/core/timing/PerformanceBase.h
index 7b9644c2dd7c819ab12964d7a9cb499ccc6d3d9e..aa3e09748c3669f5b7ce0ee5b652a9caaa61343d 100644
--- a/third_party/WebKit/Source/core/timing/PerformanceBase.h
+++ b/third_party/WebKit/Source/core/timing/PerformanceBase.h
@@ -33,6 +33,7 @@
 #define PerformanceBase_h
 
 #include "core/CoreExport.h"
+#include "core/dom/DOMHighResTimeStamp.h"
 #include "core/events/EventTarget.h"
 #include "core/timing/PerformanceEntry.h"
 #include "platform/Timer.h"
@@ -61,12 +62,20 @@ public:
     const AtomicString& interfaceName() const override;
 
     virtual PerformanceTiming* timing() const;
-    double now() const;
-
-    double timeOrigin() const { return m_timeOrigin; }
 
+    // Reduce the resolution to 5µs to prevent timing attacks. See:
+    // http://www.w3.org/TR/hr-time-2/#privacy-security
     static double clampTimeResolution(double timeSeconds);
 
+    // Translate given platform monotonic time in seconds into a high resolution
+    // DOMHighResTimeStamp in milliseconds. The result timestamp is relative to
+    // document's time origin and has a time resolution that is safe for
+    // exposing to web.
+    DOMHighResTimeStamp monotonicTimeToDOMHighResTimeStamp(double) const;
+    DOMHighResTimeStamp now() const;
+
+    double timeOrigin() const { return m_timeOrigin; }
+
     PerformanceEntryVector getEntries() const;
     PerformanceEntryVector getEntriesByType(const String& entryType);
     PerformanceEntryVector getEntriesByName(const String& name, const String& entryType);