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

Source/core/rendering/LayerPaintingInfo.h

Index: Source/core/rendering/LayerPaintingInfo.h
diff --git a/Source/core/rendering/LayerPaintingInfo.h b/Source/core/rendering/LayerPaintingInfo.h
index b9af0314271a09f01a6075c837e537846860fe1c..421e61b2f09df2591e87b19fed42344c9faf4c55 100644
--- a/Source/core/rendering/LayerPaintingInfo.h
+++ b/Source/core/rendering/LayerPaintingInfo.h
@@ -74,13 +74,12 @@ typedef unsigned PaintLayerFlags;
 struct LayerPaintingInfo {
     LayerPaintingInfo(RenderLayer* inRootLayer, const LayoutRect& inDirtyRect,
         PaintBehavior inPaintBehavior, const LayoutSize& inSubPixelAccumulation,
-        RenderObject* inPaintingRoot = 0, RenderRegion*inRegion = 0,
+        RenderObject* inPaintingRoot = 0,
         OverlapTestRequestMap* inOverlapTestRequests = 0)
         : rootLayer(inRootLayer)
         , paintingRoot(inPaintingRoot)
         , paintDirtyRect(inDirtyRect)
         , subPixelAccumulation(inSubPixelAccumulation)
-        , region(inRegion)
         , overlapTestRequests(inOverlapTestRequests)
         , paintBehavior(inPaintBehavior)
         , clipToDirtyRect(true)
@@ -89,7 +88,6 @@ struct LayerPaintingInfo {
     RenderObject* paintingRoot; // only paint descendants of this object
     LayoutRect paintDirtyRect; // relative to rootLayer;
     LayoutSize subPixelAccumulation;
-    RenderRegion* region; // May be null.
     OverlapTestRequestMap* overlapTestRequests; // May be null.
     PaintBehavior paintBehavior;
     bool clipToDirtyRect;