Monitor the intersection of video and viewport.

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

Index: third_party/WebKit/Source/core/dom/IntersectionObserver.h
diff --git a/third_party/WebKit/Source/core/dom/IntersectionObserver.h b/third_party/WebKit/Source/core/dom/IntersectionObserver.h
index 3281fcea96352ef256fc00bd74383250e40b02ac..11e424d271bd4daffee3e3db4e7c9377a5bebf31 100644
--- a/third_party/WebKit/Source/core/dom/IntersectionObserver.h
+++ b/third_party/WebKit/Source/core/dom/IntersectionObserver.h
@@ -45,6 +45,7 @@ class CORE_EXPORT IntersectionObserver final
   static IntersectionObserver* create(const IntersectionObserverInit&,
                                       IntersectionObserverCallback&,
                                       ExceptionState&);
+  // Observes any changes on intersection rect when |thresholds| is empty.
   static IntersectionObserver* create(const Vector<Length>& rootMargin,
                                       const Vector<float>& thresholds,
                                       Document*,
@@ -106,6 +107,7 @@ class CORE_EXPORT IntersectionObserver final
   Length m_bottomMargin;
   Length m_leftMargin;
   InitialState m_initialState;
+  bool m_observeViewportIntersection;
 };
 
 }  // namespace blink