Include viewport visibility checks for autoplay experiment.

Source/core/layout/LayoutView.cpp

Index: Source/core/layout/LayoutView.cpp
diff --git a/Source/core/layout/LayoutView.cpp b/Source/core/layout/LayoutView.cpp
index 45582708eaa583505b9eebc297d7b62d6199eda4..0fcb6618aa1cf06869803f11db9fbb6ea24eaedc 100644
--- a/Source/core/layout/LayoutView.cpp
+++ b/Source/core/layout/LayoutView.cpp
@@ -28,10 +28,12 @@
 #include "core/frame/Settings.h"
 #include "core/html/HTMLFrameOwnerElement.h"
 #include "core/html/HTMLIFrameElement.h"
+#include "core/html/HTMLVideoElement.h"
 #include "core/inspector/InspectorTraceEvents.h"
 #include "core/layout/HitTestResult.h"
 #include "core/layout/LayoutFlowThread.h"
 #include "core/layout/LayoutGeometryMap.h"
+#include "core/layout/LayoutMedia.h"
 #include "core/layout/LayoutPart.h"
 #include "core/layout/LayoutQuote.h"
 #include "core/layout/LayoutScrollbarPart.h"
@@ -1012,4 +1014,24 @@ void LayoutView::willBeDestroyed()
     m_compositor.clear();
 }
 
+void LayoutView::registerMediaForPositionChangeNotification(LayoutMedia* media)
+{
+    if (!m_mediaForPositionNotification.contains(media))
+        m_mediaForPositionNotification.append(media);
+}
+
+void LayoutView::unregisterMediaForPositionChangeNotification(LayoutMedia* media)
+{
+    size_t at = m_mediaForPositionNotification.find(media);
+    if (at != kNotFound)
+        m_mediaForPositionNotification.remove(at);
+}
+
+void LayoutView::sendMediaPositionChangeNotifications()
+{
+    for (auto& media : m_mediaForPositionNotification) {
+        media->notifyPositionMayHaveChanged();
+    }
+}
+
 } // namespace blink