Constify the rendering/ selection code

Source/core/rendering/RenderObject.h

Index: Source/core/rendering/RenderObject.h
diff --git a/Source/core/rendering/RenderObject.h b/Source/core/rendering/RenderObject.h
index 9442b2b35eb08eb8e2a16903012350144519f593..49911b779f06f1033a38fd8c2ceb5e6167cfeafe 100644
--- a/Source/core/rendering/RenderObject.h
+++ b/Source/core/rendering/RenderObject.h
@@ -921,7 +921,7 @@ public:
 
     // A single rectangle that encompasses all of the selected objects within this object.  Used to determine the tightest
     // possible bounding box for the selection. The rect returned is in the coordinate space of the paint invalidation container's backing.
-    virtual LayoutRect selectionRectForPaintInvalidation(const RenderLayerModelObject* /*paintInvalidationContainer*/, bool /*clipToVisibleContent*/ = true) { return LayoutRect(); }
+    virtual LayoutRect selectionRectForPaintInvalidation(const RenderLayerModelObject* /*paintInvalidationContainer*/, bool /*clipToVisibleContent*/ = true) const { return LayoutRect(); }
 
     virtual bool canBeSelectionLeaf() const { return false; }
     bool hasSelectedChildren() const { return selectionState() != SelectionNone; }