Remove frame flattening from rendering code.

Source/core/rendering/RenderFrameSet.h

Index: Source/core/rendering/RenderFrameSet.h
diff --git a/Source/core/rendering/RenderFrameSet.h b/Source/core/rendering/RenderFrameSet.h
index ac9b55e0d0f19c2ee57f482f965322870668aa5a..65701dd09231c8bc2b574897f71963faabc8d39c 100644
--- a/Source/core/rendering/RenderFrameSet.h
+++ b/Source/core/rendering/RenderFrameSet.h
@@ -110,15 +110,12 @@ private:
 
     inline HTMLFrameSetElement* frameSet() const;
 
-    bool flattenFrameSet() const;
-
     void setIsResizing(bool);
 
     void layOutAxis(GridAxis&, const Length*, int availableSpace);
     void computeEdgeInfo();
     void fillFromEdgeInfo(const FrameEdgeInfo& edgeInfo, int r, int c);
     void positionFrames();
-    void positionFramesWithFlattening();
 
     int splitPosition(const GridAxis&, int split) const;
     int hitTestSplit(const GridAxis&, int position) const;