LineBreaker doesn't need LayoutBlock(Flow) as a friend.

third_party/WebKit/Source/core/layout/LayoutBlockFlow.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003-2013 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
@@ skipping 564 matching lines @@
     LayoutUnit m_paintInvalidationLogicalBottom;
 
     bool isSelfCollapsingBlock() const override;
     bool checkIfIsSelfCollapsingBlock() const;
 
 protected:
     OwnPtr<LayoutBlockFlowRareData> m_rareData;
     OwnPtr<FloatingObjects> m_floatingObjects;
 
     friend class MarginInfo;
-    friend class LineBreaker;
     friend class LineWidth; // needs to know FloatingObject
 
 // FIXME-BLOCKFLOW: These methods have implementations in
 // LayoutBlockFlowLine. They should be moved to the proper header once the
 // line layout code is separated from LayoutBlock and LayoutBlockFlow.
 // START METHODS DEFINED IN LayoutBlockFlowLine
 private:
     InlineFlowBox* createLineBoxes(LineLayoutItem, const LineInfo&, InlineBox* childBox);
     RootInlineBox* constructLine(BidiRunList<BidiRun>&, const LineInfo&);
     void setMarginsForRubyRun(BidiRun*, LayoutRubyRun*, LayoutObject*, const LineInfo&);
@@ skipping 25 matching lines @@
 
 // END METHODS DEFINED IN LayoutBlockFlowLine
 
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutBlockFlow, isLayoutBlockFlow());
 
 } // namespace blink
 
 #endif // LayoutBlockFlow_h