Include viewport visibility checks for autoplay experiment.

Source/core/html/HTMLMediaElement.cpp

Index: Source/core/html/HTMLMediaElement.cpp
diff --git a/Source/core/html/HTMLMediaElement.cpp b/Source/core/html/HTMLMediaElement.cpp
index 29a86fab5d351a6259f51afc3281ff921a8d588e..c417c0d6eb105338e6a868117656abb9815fe1b7 100644
--- a/Source/core/html/HTMLMediaElement.cpp
+++ b/Source/core/html/HTMLMediaElement.cpp
@@ -3744,6 +3744,16 @@ void HTMLMediaElement::setInitialPlayWithoutUserGestures(bool value)
     m_initialPlayWithoutUserGesture = value;
 }
 
+void HTMLMediaElement::notifyPositionMayHaveChanged()
+{
+    m_autoplayHelper.positionChanged();
+}
+
+void HTMLMediaElement::triggerAutoplayViewportCheck()
+{
+    m_autoplayHelper.triggerAutoplayViewportCheck();
+}
+
 #if ENABLE(WEB_AUDIO)
 void HTMLMediaElement::clearWeakMembers(Visitor* visitor)
 {