[New Multicolumn] Add support for column-span:all

Source/core/rendering/RenderPagedFlowThread.h

Index: Source/core/rendering/RenderPagedFlowThread.h
diff --git a/Source/core/rendering/RenderPagedFlowThread.h b/Source/core/rendering/RenderPagedFlowThread.h
index d20d7bb32c8935a03488e8b1384d6a699ca73d12..60be170ce10d613ab220fb72e2515297d2713ba3 100644
--- a/Source/core/rendering/RenderPagedFlowThread.h
+++ b/Source/core/rendering/RenderPagedFlowThread.h
@@ -20,11 +20,13 @@ public:
     RenderBlockFlow* pagedBlockFlow() const { return toRenderBlockFlow(parent()); }
 
     virtual bool isRenderPagedFlowThread() const OVERRIDE { return true; }
-    virtual bool heightIsAuto() const OVERRIDE { return !columnHeightAvailable(); }
     virtual const char* renderName() const OVERRIDE;
     virtual bool needsNewWidth() const OVERRIDE;
     virtual void updateLogicalWidth() OVERRIDE;
     virtual void layout();
+
+private:
+    virtual bool isDescendantValidColumnSpanner(RenderObject* /*descendant*/) const OVERRIDE { return false; }
 };
 
 } // namespace blink