[New Multicolumn] Layout support for column-span:all.

Source/core/rendering/RenderMultiColumnSpannerPlaceholder.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef RenderMultiColumnSpannerPlaceholder_h
 #define RenderMultiColumnSpannerPlaceholder_h
 
 #include "core/rendering/RenderMultiColumnFlowThread.h"
 
 namespace blink {
@@ skipping 11 matching lines @@
     RenderFlowThread* flowThread() const { return toRenderBlockFlow(parent())->multiColumnFlowThread(); }
 
     RenderBox* rendererInFlowThread() const { return m_rendererInFlowThread; }
     void setRendererInFlowThread(RenderBox* renderer) { m_rendererInFlowThread = renderer; }
     void spannerWillBeRemoved();
 
 protected:
     virtual void willBeRemovedFromTree() override;
     virtual bool needsPreferredWidthsRecalculation() const override;
     virtual void layout() override;
+    virtual void computeLogicalHeight(LayoutUnit logicalHeight, LayoutUnit logicalTop, LogicalExtentComputedValues&) const override;
     virtual void invalidateTreeIfNeeded(const PaintInvalidationState&) override;
+    virtual void paint(const PaintInfo&, const LayoutPoint& paintOffset) override;
+    virtual bool nodeAtPoint(const HitTestRequest&, HitTestResult&, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction) override;
     virtual const char* renderName() const override;
 
 private:
     RenderMultiColumnSpannerPlaceholder(RenderBox*);
 
     RenderBox* m_rendererInFlowThread; // The actual column-span:all renderer inside the flow thread.
 };
 
 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderMultiColumnSpannerPlaceholder, isRenderMultiColumnSpannerPlaceholder());
 
 } // namespace blink
 
 #endif