Implement lazy block layout prototype behind a runtime flag.

Source/core/rendering/RenderView.h

Index: Source/core/rendering/RenderView.h
diff --git a/Source/core/rendering/RenderView.h b/Source/core/rendering/RenderView.h
index d7e16c2747213229ae650a75ca17a7531db068a2..4bc96fea0e3e84fab0ed1a89fa474416e5efa2fe 100644
--- a/Source/core/rendering/RenderView.h
+++ b/Source/core/rendering/RenderView.h
@@ -32,6 +32,7 @@ namespace WebCore {
 
 class FlowThreadController;
 class RenderLayerCompositor;
+class RenderLazyBlock;
 class RenderQuote;
 class RenderWidget;
 
@@ -203,6 +204,10 @@ public:
     void setRenderQuoteHead(RenderQuote* head) { m_renderQuoteHead = head; }
     RenderQuote* renderQuoteHead() const { return m_renderQuoteHead; }
 
+    void setFirstLazyBlock(RenderLazyBlock* block) { m_firstLazyBlock = block; }
+    RenderLazyBlock* firstLazyBlock() const { return m_firstLazyBlock; }
+    void markLazyBlocksForLayout();
+
     // FIXME: This is a work around because the current implementation of counters
     // requires walking the entire tree repeatedly and most pages don't actually use either
     // feature so we shouldn't take the performance hit when not needed. Long term we should
@@ -318,6 +323,7 @@ private:
     OwnPtr<FlowThreadController> m_flowThreadController;
     RefPtr<IntervalArena> m_intervalArena;
 
+    RenderLazyBlock* m_firstLazyBlock;
     RenderQuote* m_renderQuoteHead;
     unsigned m_renderCounterCount;
 };