Fix 'text-underline-position: under' to use em height ascent/descent

third_party/WebKit/Source/core/layout/line/InlineTextBox.h

 /*
  * (C) 1999 Lars Knoll (knoll@kde.org)
  * (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2009, 2010, 2011 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.
@@ skipping 81 matching lines @@
                                     const InlineTextBox* second) {
     return first->Start() < second->Start();
   }
 
   int BaselinePosition(FontBaseline) const final;
   LayoutUnit LineHeight() const final;
 
   bool GetEmphasisMarkPosition(const ComputedStyle&,
                                TextEmphasisPosition&) const;
 
+  LayoutUnit OffsetTo(LineVerticalPositionType, FontBaseline) const;
+  LayoutUnit VerticalPosition(LineVerticalPositionType, FontBaseline) const;
+
   LayoutRect LogicalOverflowRect() const;
   void SetLogicalOverflowRect(const LayoutRect&);
   LayoutUnit LogicalTopVisualOverflow() const {
     return LogicalOverflowRect().Y();
   }
   LayoutUnit LogicalBottomVisualOverflow() const {
     return LogicalOverflowRect().MaxY();
   }
 
   // charactersWithHyphen, if provided, must not be destroyed before the
@@ skipping 128 matching lines @@
            (Expansion() && NextLeafChild() ? TextRun::kAllowTrailingExpansion
                                            : TextRun::kForbidTrailingExpansion);
   }
 };
 
 DEFINE_INLINE_BOX_TYPE_CASTS(InlineTextBox);
 
 }  // namespace blink
 
 #endif  // InlineTextBox_h