Calculate Underline thickness for Skia from Font metrics

core/SkPaint.cpp

Index: core/SkPaint.cpp
diff --git a/core/SkPaint.cpp b/core/SkPaint.cpp
index af032d001e51342be8c1997d7fae92a8520ef08c..0b3d56c7c570a79ec1e2dbc846caaf5d30f75186 100644
--- a/core/SkPaint.cpp
+++ b/core/SkPaint.cpp
@@ -1296,6 +1296,7 @@ SkScalar SkPaint::getFontMetrics(FontMetrics* metrics, SkScalar zoom) const {
         metrics->fXMin = SkScalarMul(metrics->fXMin, scale);
         metrics->fXMax = SkScalarMul(metrics->fXMax, scale);
         metrics->fXHeight = SkScalarMul(metrics->fXHeight, scale);
+        metrics->fUnderlineThickness = SkScalarMul(metrics->fUnderlineThickness, scale);
     }
     return metrics->fDescent - metrics->fAscent + metrics->fLeading;
 }