Fix underline position and thickness calculation

Source/platform/fonts/skia/SimpleFontDataSkia.cpp

 /*
  * Copyright (c) 2008, 2009, 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
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 113 matching lines @@
     } else {
         xHeight = ascent * 0.56; // Best guess from Windows font metrics.
         m_fontMetrics.setXHeight(xHeight);
         m_fontMetrics.setHasXHeight(false);
     }
 
     float lineGap = SkScalarToFloat(metrics.fLeading);
     m_fontMetrics.setLineGap(lineGap);
     m_fontMetrics.setLineSpacing(lroundf(ascent) + lroundf(descent) + lroundf(lineGap));
 
-    float underlineThickness = SkScalarToFloat(metrics.fUnderlineThickness);
-    m_fontMetrics.setUnderlineThickness(underlineThickness);
-
-    float underlinePosition = SkScalarToFloat(metrics.fUnderlinePosition);
-    m_fontMetrics.setUnderlineThickness(underlinePosition);
+    SkScalar underlineThickness, underlinePosition;
+    if (metrics.hasUnderlineThickness(&underlineThickness)
+        && metrics.hasUnderlinePosition(&underlinePosition)) {
+        m_fontMetrics.setUnderlineThickness(SkScalarToFloat(underlineThickness));
+        m_fontMetrics.setUnderlinePosition(SkScalarToFloat(-underlinePosition));
+    }
 
     if (platformData().orientation() == Vertical && !isTextOrientationFallback()) {
         static const uint32_t vheaTag = SkSetFourByteTag('v', 'h', 'e', 'a');
         static const uint32_t vorgTag = SkSetFourByteTag('V', 'O', 'R', 'G');
         size_t vheaSize = face->getTableSize(vheaTag);
         size_t vorgSize = face->getTableSize(vorgTag);
         if ((vheaSize > 0) || (vorgSize > 0))
             m_hasVerticalGlyphs = true;
     }
 
@@ skipping 149 matching lines @@
         if (glyphs[i]) {
             pageToFill->setGlyphDataForIndex(offset + i, glyphs[i], this);
             haveGlyphs = true;
         }
     }
 
     return haveGlyphs;
 }
 
 } // namespace WebCore