List marker pseudo elements.

Source/core/html/HTMLOListElement.cpp

Index: Source/core/html/HTMLOListElement.cpp
diff --git a/Source/core/html/HTMLOListElement.cpp b/Source/core/html/HTMLOListElement.cpp
index 4da5176a545b3d09689ce83c8e5da11c6da56275..4698aef14c8851fb1a147802ca15ec8f5d047a55 100644
--- a/Source/core/html/HTMLOListElement.cpp
+++ b/Source/core/html/HTMLOListElement.cpp
@@ -108,4 +108,21 @@ void HTMLOListElement::recalculateItemCount()
     m_shouldRecalculateItemCount = false;
 }
 
+void HTMLOListElement::attach(const AttachContext& context)
+{
+    HTMLElement::attach(context);
+
+    if (!RuntimeEnabledFeatures::listMarkerPseudoElementEnabled())
+        return;
+
+    if (!m_isReversed)
+        return;
+
+    // If we're looking at a reversed ordered list we have to recalculate
+    // all of the marker values after everything is inserted. This is because
+    // we built the tree top to bottom, but that means the list item with the
+    // highest value will end up with 1 and we count down from there.
+    updateItemValues();
+}
+
 }