*** DO NOT LAND *** Attempt to understand Regions complexity

Source/core/rendering/RenderLayer.h

Index: Source/core/rendering/RenderLayer.h
diff --git a/Source/core/rendering/RenderLayer.h b/Source/core/rendering/RenderLayer.h
index 7d2152257b022b8d85e5938ac4d759a32f054c4c..511a00f1a371ec54f9e0a8d693213ac5b3c53f31 100644
--- a/Source/core/rendering/RenderLayer.h
+++ b/Source/core/rendering/RenderLayer.h
@@ -66,7 +66,6 @@ class FilterOperations;
 class HitTestRequest;
 class HitTestResult;
 class HitTestingTransformState;
-class RenderFlowThread;
 class RenderGeometryMap;
 class CompositedLayerMapping;
 class RenderLayerCompositor;
@@ -259,8 +258,7 @@ public:
     // paints the layers that intersect the damage rect from back to
     // front.  The hitTest method looks for mouse events by walking
     // layers that intersect the point from front to back.
-    void paint(GraphicsContext*, const LayoutRect& damageRect, PaintBehavior = PaintBehaviorNormal, RenderObject* paintingRoot = 0,
-        RenderRegion* = 0, PaintLayerFlags = 0);
+    void paint(GraphicsContext*, const LayoutRect& damageRect, PaintBehavior = PaintBehaviorNormal, RenderObject* paintingRoot = 0, PaintLayerFlags = 0);
     bool hitTest(const HitTestRequest&, HitTestResult&);
     bool hitTest(const HitTestRequest&, const HitTestLocation&, HitTestResult&);
     void paintOverlayScrollbars(GraphicsContext*, const LayoutRect& damageRect, PaintBehavior, RenderObject* paintingRoot = 0);
@@ -413,8 +411,6 @@ public:
     void setViewportConstrainedNotCompositedReason(ViewportConstrainedNotCompositedReason reason) { m_compositingProperties.viewportConstrainedNotCompositedReason = reason; }
     ViewportConstrainedNotCompositedReason viewportConstrainedNotCompositedReason() const { return static_cast<ViewportConstrainedNotCompositedReason>(m_compositingProperties.viewportConstrainedNotCompositedReason); }
 
-    bool isOutOfFlowRenderFlowThread() const { return renderer()->isOutOfFlowRenderFlowThread(); }
-
     bool scrollsWithRespectTo(const RenderLayer*) const;
 
     void addLayerHitTestRects(LayerHitTestRects&) const;
@@ -497,7 +493,7 @@ private:
     void paintPaginatedChildLayer(RenderLayer* childLayer, GraphicsContext*, const LayerPaintingInfo&, PaintLayerFlags);
     void paintChildLayerIntoColumns(RenderLayer* childLayer, GraphicsContext*, const LayerPaintingInfo&, PaintLayerFlags, const Vector<RenderLayer*>& columnLayers, size_t columnIndex);
 
-    void collectFragments(LayerFragments&, const RenderLayer* rootLayer, RenderRegion*, const LayoutRect& dirtyRect,
+    void collectFragments(LayerFragments&, const RenderLayer* rootLayer, const LayoutRect& dirtyRect,
         ClipRectsType, OverlayScrollbarSizeRelevancy inOverlayScrollbarSizeRelevancy = IgnoreOverlayScrollbarSize,
         ShouldRespectOverflowClip = RespectOverflowClip, const LayoutPoint* offsetFromRoot = 0,
         const LayoutSize& subPixelAccumulation = LayoutSize(), const LayoutRect* layerBoundingBox = 0);
@@ -576,9 +572,6 @@ private:
 
     void updatePagination();
 
-    // FIXME: Temporary. Remove when new columns come online.
-    bool useRegionBasedColumns() const;
-
     bool hasCompositingDescendant() const { return m_compositingProperties.hasCompositingDescendant; }
     void setHasCompositingDescendant(bool b)  { m_compositingProperties.hasCompositingDescendant = b; }