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

Source/core/layout/api/LineLayoutItem.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef LineLayoutItem_h
 #define LineLayoutItem_h
 
 #include "core/layout/LayoutObject.h"
 #include "core/layout/LayoutObjectInlines.h"
 
 #include "platform/LayoutUnit.h"
 
 namespace blink {
 
 class ComputedStyle;
 class Document;
 class HitTestRequest;
 class HitTestLocation;
 class LayoutObject;
 class LineLayoutBox;
 class LineLayoutBoxModel;
+class LineLayoutPaintShim;
 
 enum HitTestFilter;
 
 class LineLayoutItem {
 public:
     explicit LineLayoutItem(LayoutObject* layoutObject)
         : m_layoutObject(layoutObject)
     {
     }
 
@@ skipping 284 matching lines @@
     }
 
 #endif
 
 protected:
     LayoutObject* layoutObject() { return m_layoutObject; }
     const LayoutObject* layoutObject() const { return m_layoutObject; }
 
 private:
     LayoutObject* m_layoutObject;
+
+    friend class LineLayoutPaintShim;
 };
 
 } // namespace blink
 
 #endif // LineLayoutItem_h