[New Multicolumn] Support for block direction margins on spanners.

Source/core/rendering/RenderMultiColumnSpannerPlaceholder.h

Index: Source/core/rendering/RenderMultiColumnSpannerPlaceholder.h
diff --git a/Source/core/rendering/RenderMultiColumnSpannerPlaceholder.h b/Source/core/rendering/RenderMultiColumnSpannerPlaceholder.h
index 28173449687145e4c6cd709d7d4eaec633d5dfa6..28770c6b758403c88e54285f84509a6f8fe15ee0 100644
--- a/Source/core/rendering/RenderMultiColumnSpannerPlaceholder.h
+++ b/Source/core/rendering/RenderMultiColumnSpannerPlaceholder.h
@@ -24,6 +24,7 @@ public:
     RenderBox* rendererInFlowThread() const { return m_rendererInFlowThread; }
     void setRendererInFlowThread(RenderBox* renderer) { m_rendererInFlowThread = renderer; }
     void spannerWillBeRemoved();
+    void updateMarginProperties();
 
 protected:
     virtual void willBeRemovedFromTree() override;