[Line Layout API] Add shim for Paint objects to access underlying LayoutObject

Source/core/layout/api/LineLayoutItem.h

Index: Source/core/layout/api/LineLayoutItem.h
diff --git a/Source/core/layout/api/LineLayoutItem.h b/Source/core/layout/api/LineLayoutItem.h
index 68771eecb0ee19641320a26212476cdaba8785ab..bbab3a94c8a5f5df5e4ab11aca5c26e7a67d1909 100644
--- a/Source/core/layout/api/LineLayoutItem.h
+++ b/Source/core/layout/api/LineLayoutItem.h
@@ -19,6 +19,7 @@ class HitTestLocation;
 class LayoutObject;
 class LineLayoutBox;
 class LineLayoutBoxModel;
+class LineLayoutPaintShim;
 
 enum HitTestFilter;
 
@@ -323,6 +324,8 @@ protected:
 
 private:
     LayoutObject* m_layoutObject;
+
+    friend class LineLayoutPaintShim;
 };
 
 } // namespace blink