Use DOMHighResTimeStamp for notification time.

third_party/WebKit/Source/core/dom/IntersectionObservation.cpp

 // Copyright 2016 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.
 
 #include "core/dom/IntersectionObservation.h"
 
 #include "core/dom/ElementRareData.h"
 #include "core/dom/IntersectionObserver.h"
 #include "core/frame/FrameView.h"
 #include "core/layout/LayoutBox.h"
@@ skipping 104 matching lines @@
     clipToFrameView(geometry);
 
     if (geometry.intersectionRect.size().isZero())
         geometry.intersectionRect = LayoutRect();
     if (!m_shouldReportRootBounds)
         geometry.rootRect = LayoutRect();
 
     return true;
 }
 
-void IntersectionObservation::computeIntersectionObservations(double timestamp)
+void IntersectionObservation::computeIntersectionObservations(DOMHighResTimeStamp timestamp)
 {
     // Pre-oilpan, there will be a delay between the time when the target Element gets deleted
     // (because its ref count dropped to zero) and when this IntersectionObservation gets
     // deleted (during the next gc run, because the target Element is the only thing keeping
     // the IntersectionObservation alive).  During that interval, we need to check that m_target
     // hasn't been cleared.
     Element* targetElement = target();
     if (!targetElement || !isActive())
         return;
     LayoutObject* targetLayoutObject = targetElement->layoutObject();
     // TODO(szager): Support SVG
     if (!targetLayoutObject || (!targetLayoutObject->isBox() && !targetLayoutObject->isInline()))
         return;
 
     IntersectionGeometry geometry;
     if (!computeGeometry(geometry))
         return;
 
     float intersectionArea = geometry.intersectionRect.size().width().toFloat() * geometry.intersectionRect.size().height().toFloat();
     float targetArea = geometry.targetRect.size().width().toFloat() * geometry.targetRect.size().height().toFloat();
     if (!targetArea)
         return;
     float newVisibleRatio = intersectionArea / targetArea;
     unsigned newThresholdIndex = observer().firstThresholdGreaterThan(newVisibleRatio);
     if (m_lastThresholdIndex != newThresholdIndex) {
         IntersectionObserverEntry* newEntry = new IntersectionObserverEntry(
-            timestamp / 1000.0,
+            timestamp,

[ojan, 2016/01/22 19:24:10]

I think you need to change IntersectionObserverEntry to store a
DOMHighResTimeStamp as well?

[szager1, 2016/02/02 18:07:51]

Done.

             pixelSnappedIntRect(geometry.targetRect),
             pixelSnappedIntRect(geometry.rootRect),
             pixelSnappedIntRect(geometry.intersectionRect),
             targetElement);
         observer().enqueueIntersectionObserverEntry(*newEntry);
     }
     setLastThresholdIndex(newThresholdIndex);
 }
 
 void IntersectionObservation::disconnect()
@@ skipping 10 matching lines @@
     m_observer.clear();
 }
 
 DEFINE_TRACE(IntersectionObservation)
 {
     visitor->trace(m_observer);
     visitor->trace(m_target);
 }
 
 } // namespace blink