Monitor the intersection of video and viewport.

third_party/WebKit/Source/core/dom/ElementVisibilityObserver.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 ElementVisibilityObserver_h
 #define ElementVisibilityObserver_h
 
 #include "core/CoreExport.h"
 #include "core/dom/IntersectionObserver.h"
 #include "platform/heap/Heap.h"
@@ skipping 16 matching lines @@
     : public GarbageCollectedFinalized<ElementVisibilityObserver> {
   WTF_MAKE_NONCOPYABLE(ElementVisibilityObserver);
 
  public:
   using VisibilityCallback = Function<void(bool), WTF::SameThreadAffinity>;
 
   ElementVisibilityObserver(Element*, std::unique_ptr<VisibilityCallback>);
   virtual ~ElementVisibilityObserver();
 
   void start();
+  void start(const Vector<float>& thresholds);
   void stop();
 
   void deliverObservationsForTesting();
 
+  float ratio() { return m_ratio; }
+
   DECLARE_VIRTUAL_TRACE();
 
  private:
   class ElementVisibilityCallback;
 
   void onVisibilityChanged(
       const HeapVector<Member<IntersectionObserverEntry>>&);
 
   Member<Element> m_element;
   Member<IntersectionObserver> m_intersectionObserver;
   std::unique_ptr<VisibilityCallback> m_callback;
+  float m_ratio = 0;
 };
 
 }  // namespace blink
 
 #endif  // ElementVisibilityObserver_h