Remove CSS regions support, keeping a bare minimum to support "region-based" multicol.

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 5f3161633db7b8c6e36d398fbcc476d4a713c162..908d2d990a15998aaf743d66c31a8b467e1bd434 100644
--- a/Source/core/rendering/RenderLayer.h
+++ b/Source/core/rendering/RenderLayer.h
@@ -277,8 +277,7 @@ 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);
@@ -524,7 +523,7 @@ 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);