Underline Thickness is not uniform

Source/core/rendering/InlineFlowBox.h

 /*
  * Copyright (C) 2003, 2004, 2005, 2006, 2007 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 97 matching lines @@
     virtual void clearTruncation() OVERRIDE;
 
     IntRect roundedFrameRect() const;
 
     void paintBoxDecorations(PaintInfo&, const LayoutPoint&);
     void paintMask(PaintInfo&, const LayoutPoint&);
     void paintFillLayers(const PaintInfo&, const Color&, const FillLayer*, const LayoutRect&, CompositeOperator = CompositeSourceOver);
     void paintFillLayer(const PaintInfo&, const Color&, const FillLayer*, const LayoutRect&, CompositeOperator = CompositeSourceOver);
     void paintBoxShadow(const PaintInfo&, RenderStyle*, ShadowStyle, const LayoutRect&);
     virtual void paint(PaintInfo&, const LayoutPoint&, LayoutUnit lineTop, LayoutUnit lineBottom) OVERRIDE;
+    virtual void paintDecorationStyle(PaintInfo&, const LayoutPoint&, LayoutUnit lineTop, LayoutUnit lineBottom, float decorationThickness) { };
+    virtual void getPaintDecorationSyle(PaintInfo&, const LayoutPoint&, float *) { };
     virtual bool nodeAtPoint(const HitTestRequest&, HitTestResult&, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, LayoutUnit lineTop, LayoutUnit lineBottom) OVERRIDE;
 
     bool boxShadowCanBeAppliedToBackground(const FillLayer&) const;
 
     virtual RenderLineBoxList* rendererLineBoxes() const;
 
     // logicalLeft = left in a horizontal line and top in a vertical line.
     LayoutUnit marginBorderPaddingLogicalLeft() const { return marginLogicalLeft() + borderLogicalLeft() + paddingLogicalLeft(); }
     LayoutUnit marginBorderPaddingLogicalRight() const { return marginLogicalRight() + borderLogicalRight() + paddingLogicalRight(); }
     LayoutUnit marginLogicalLeft() const
@@ skipping 239 matching lines @@
 }
 
 } // namespace WebCore
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showTree(const WebCore::InlineFlowBox*);
 #endif
 
 #endif // InlineFlowBox_h