[CSS Regions] Elements in a region should be assignable to a named flow

Source/core/dom/PseudoElement.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Neither the name of Google Inc. nor the names of its
@@ skipping 27 matching lines @@
     static PassRefPtr<PseudoElement> create(Element* parent, PseudoId pseudoId)
     {
         return adoptRef(new PseudoElement(parent, pseudoId));
     }
     ~PseudoElement();
 
     virtual PassRefPtr<RenderStyle> customStyleForRenderer() OVERRIDE;
     virtual void attach(const AttachContext& = AttachContext()) OVERRIDE;
     virtual bool rendererIsNeeded(const NodeRenderingContext&) OVERRIDE;
 
+    // As per http://dev.w3.org/csswg/css3-regions/#flow-into, pseudo-elements such as ::first-line, ::first-letter, ::before or ::after
+    // cannot be directly collected into a named flow.
+    virtual bool shouldMoveToFlowThread(RenderStyle*) const OVERRIDE { return false; }
+
     virtual bool canStartSelection() const OVERRIDE { return false; }
     virtual bool canContainRangeEndPoint() const OVERRIDE { return false; }
 
     static String pseudoElementNameForEvents(PseudoId);
 
 private:
     PseudoElement(Element*, PseudoId);
 
     virtual void didRecalcStyle(StyleChange) OVERRIDE;
     virtual PseudoId customPseudoId() const OVERRIDE { return m_pseudoId; }
 
     PseudoId m_pseudoId;
 };
 
 const QualifiedName& pseudoElementTagName();
 
 inline bool pseudoElementRendererIsNeeded(const RenderStyle* style)
 {
     return style && style->display() != NONE && (style->contentData() || !style->regionThread().isEmpty());
 }
 
 } // namespace
 
 #endif