Implement suspend/resume for IntersectionObserver notifications.

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

 // 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.
 
 #ifndef IntersectionObserver_h
 #define IntersectionObserver_h
 
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/dom/Element.h"
 #include "core/dom/IntersectionObservation.h"
@@ skipping 24 matching lines @@
     Element* root() { return m_root.get(); }
     LayoutObject* rootLayoutObject();
     bool isDescendantOfRoot(const Element*) const;
     void computeIntersectionObservations(double timestamp);
     void enqueueIntersectionObserverEntry(IntersectionObserverEntry&);
     unsigned firstThresholdGreaterThan(float ratio) const;
     void deliver();
     void setActive(bool);
     void disconnect();
     void removeObservation(IntersectionObservation&);
+    bool hasEntries() const { return m_entries.size(); }
 
     DECLARE_TRACE();
 
 private:
     explicit IntersectionObserver(IntersectionObserverCallback&, Element&, const Vector<float>& thresholds);
 
     void checkRootAndDetachIfNeeded();
 
     Member<IntersectionObserverCallback> m_callback;
     WeakPtrWillBeWeakMember<Element> m_root;
     HeapHashSet<WeakMember<IntersectionObservation>> m_observations;
     HeapVector<Member<IntersectionObserverEntry>> m_entries;
     Vector<float> m_thresholds;
 };
 
 } // namespace blink
 
 #endif // IntersectionObserver_h