Calculate Underline thickness for Skia from Font metrics

ports/SkFontHost_FreeType.cpp

Index: ports/SkFontHost_FreeType.cpp
diff --git a/ports/SkFontHost_FreeType.cpp b/ports/SkFontHost_FreeType.cpp
index 97046f4ba89fda49c264225fd9f5ae76b0fa34e6..2a524e71efde0aafc374fbf4b1ebe9cd95bc40b6 100644
--- a/ports/SkFontHost_FreeType.cpp
+++ b/ports/SkFontHost_FreeType.cpp
@@ -1385,6 +1385,7 @@ void SkScalerContext_FreeType::generateFontMetrics(SkPaint::FontMetrics* mx,
 
     // pull from format-specific metrics as needed
     SkScalar ascent, descent, leading, xmin, xmax, ymin, ymax;
+    SkScalar underlineThickness;
     if (face->face_flags & FT_FACE_FLAG_SCALABLE) { // scalable outline font
         ascent = -SkIntToScalar(face->ascender) / upem;
         descent = -SkIntToScalar(face->descender) / upem;
@@ -1393,6 +1394,7 @@ void SkScalerContext_FreeType::generateFontMetrics(SkPaint::FontMetrics* mx,
         xmax = SkIntToScalar(face->bbox.xMax) / upem;
         ymin = -SkIntToScalar(face->bbox.yMin) / upem;
         ymax = -SkIntToScalar(face->bbox.yMax) / upem;
+        underlineThickness = SkIntToScalar(face->underline_thickness)/upem;
         // we may be able to synthesize x_height and cap_height from outline
         if (!x_height) {
             FT_BBox bbox;
@@ -1448,6 +1450,7 @@ void SkScalerContext_FreeType::generateFontMetrics(SkPaint::FontMetrics* mx,
         mx->fXMax = xmax;
         mx->fXHeight = x_height;
         mx->fCapHeight = cap_height;
+        mx->fUnderlineThickness = underlineThickness;
     }
     if (my) {
         my->fTop = ymax * myy;
@@ -1460,6 +1463,7 @@ void SkScalerContext_FreeType::generateFontMetrics(SkPaint::FontMetrics* mx,
         my->fXMax = xmax;
         my->fXHeight = x_height;
         my->fCapHeight = cap_height;
+        my->fUnderlineThickness = underlineThickness;
     }
 }