Remove some unused paint invalidation members from RenderObject.

sky/engine/core/rendering/RenderBlockFlow.h

Index: sky/engine/core/rendering/RenderBlockFlow.h
diff --git a/sky/engine/core/rendering/RenderBlockFlow.h b/sky/engine/core/rendering/RenderBlockFlow.h
index a58f8cb359183535ce83e61b1fb8df1fdd55fa6b..d0bf8fe077f7431a6f44502751247f0c655d8591 100644
--- a/sky/engine/core/rendering/RenderBlockFlow.h
+++ b/sky/engine/core/rendering/RenderBlockFlow.h
@@ -115,7 +115,7 @@ public:
     }
 
 protected:
-    virtual void layoutChildren(bool relayoutChildren, SubtreeLayoutScope&, LayoutUnit& paintInvalidationLogicalTop, LayoutUnit& paintInvalidationLogicalBottom, LayoutUnit beforeEdge, LayoutUnit afterEdge);
+    virtual void layoutChildren(bool relayoutChildren, SubtreeLayoutScope&, LayoutUnit beforeEdge, LayoutUnit afterEdge);
 
     virtual bool updateLogicalWidthAndColumnWidth() override;
 
@@ -143,10 +143,6 @@ public:
         bool everHadLayout;
     };
 
-private:
-    LayoutUnit m_paintInvalidationLogicalTop;
-    LayoutUnit m_paintInvalidationLogicalBottom;
-
 protected:
     friend class BreakingContext; // FIXME: It uses insertFloatingObject and positionNewFloatOnLine, if we move those out from the private scope/add a helper to LineBreaker, we can remove this friend
     friend class LineBreaker;