[New Multicolumn] Support for paged overflow.

Source/core/rendering/RenderFlowThread.h

 /*
  * Copyright (C) 2011 Adobe Systems Incorporated. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above
  *    copyright notice, this list of conditions and the following
  *    disclaimer.
@@ skipping 41 matching lines @@
 // and nodeAtPoint methods to this object. Each RenderRegion will actually be a viewPort
 // of the RenderFlowThread.
 
 class RenderFlowThread: public RenderBlockFlow {
 public:
     RenderFlowThread();
     virtual ~RenderFlowThread() { };
 
     virtual bool isRenderFlowThread() const OVERRIDE FINAL { return true; }
     virtual bool isRenderMultiColumnFlowThread() const { return false; }
+    virtual bool isRenderPagedFlowThread() const { return false; }
 
     virtual void layout() OVERRIDE;
 
     // Always create a RenderLayer for the RenderFlowThread so that we
     // can easily avoid drawing the children directly.
     virtual LayerType layerTypeRequired() const OVERRIDE FINAL { return NormalLayer; }
 
     virtual bool nodeAtPoint(const HitTestRequest&, HitTestResult&, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction) OVERRIDE FINAL;
 
     virtual void addRegionToThread(RenderRegion*) = 0;
@@ skipping 143 matching lines @@
 };
 
 template <> struct ValueToString<RenderRegion*> {
     static String string(const RenderRegion* value) { return String::format("%p", value); }
 };
 #endif
 
 } // namespace WebCore
 
 #endif // RenderFlowThread_h