List marker pseudo elements.

Source/core/layout/LayoutListMarker.h

Index: Source/core/layout/LayoutListMarker.h
diff --git a/Source/core/layout/LayoutListMarker.h b/Source/core/layout/LayoutListMarker.h
index de8ce914b4b39342dce905f22ab86799c908b610..8967ad318ebf4df0dd821d8b9839aac9c5a2ccec 100644
--- a/Source/core/layout/LayoutListMarker.h
+++ b/Source/core/layout/LayoutListMarker.h
@@ -31,11 +31,12 @@ class LayoutListItem;
 
 String listMarkerText(EListStyleType, int value);
 
-// Used to render the list item's marker.
+// Used to layout the list item's marker.
 // The LayoutListMarker always has to be a child of a LayoutListItem.
 class LayoutListMarker final : public LayoutBox {
 public:
     static LayoutListMarker* createAnonymous(LayoutListItem*);
+    LayoutListMarker(Element*, LayoutListItem*);
 
     virtual ~LayoutListMarker();
     virtual void destroy() override;
@@ -50,7 +51,8 @@ public:
     LayoutRect localSelectionRect();
     virtual bool isImage() const override;
     const StyleImage* image() { return m_image.get(); }
-    const LayoutListItem* listItem() { return m_listItem; }
+    const LayoutListItem* listItem() const { return m_listItem; }
+    LayoutListItem* mutableListItem() const { return m_listItem; }
 
     static UChar listMarkerSuffix(EListStyleType, int value);