[New Multicolumn] Actual support for layout of column-span:all.

Source/core/rendering/RenderObject.h

Index: Source/core/rendering/RenderObject.h
diff --git a/Source/core/rendering/RenderObject.h b/Source/core/rendering/RenderObject.h
index 6fbfd292742396ac3e6073297d0653faec32dcf7..7d6eedcce8d1b56968175614ef8e6e684db62203 100644
--- a/Source/core/rendering/RenderObject.h
+++ b/Source/core/rendering/RenderObject.h
@@ -300,6 +300,9 @@ private:
     void addAbsoluteRectForLayer(LayoutRect& result);
     bool requiresAnonymousTableWrappers(const RenderObject*) const;
 
+    // This renderer has column-span:all, but is it really a valid column spanner?
+    bool isValidColumnSpanAll() const;
+
     // Gets pseudoStyle from Shadow host(in case of input elements)
     // or from Parent element.
     PassRefPtr<RenderStyle> getUncachedPseudoStyleFromParentOrShadowHost() const;
@@ -386,6 +389,7 @@ public:
     virtual bool isRenderBlock() const { return false; }
     virtual bool isRenderBlockFlow() const { return false; }
     virtual bool isRenderFlowThread() const { return false; }
+    virtual bool isRenderMultiColumnFlowThread() const { return false; }
     virtual bool isRenderInline() const { return false; }
     virtual bool isRenderPart() const { return false; }
 
@@ -634,6 +638,8 @@ public:
     Document& document() const { return m_node->document(); }
     LocalFrame* frame() const { return document().frame(); }
 
+    bool isColumnSpanAll() const { return style()->columnSpan() == ColumnSpanAll && isValidColumnSpanAll(); }
+
     // Returns the object containing this one. Can be different from parent for positioned elements.
     // If paintInvalidationContainer and paintInvalidationContainerSkipped are not null, on return *paintInvalidationContainerSkipped
     // is true if the renderer returned is an ancestor of paintInvalidationContainer.