Adding code to calculate Underline Thickness from Font Metrics, this will be useful when Skia is us…

src/ports/SkFontHost_win_dw.cpp

Index: src/ports/SkFontHost_win_dw.cpp
diff --git a/src/ports/SkFontHost_win_dw.cpp b/src/ports/SkFontHost_win_dw.cpp
index b9f69bdb3ca26857be1acb5dec13a829d648d05e..598c287711bc4b0d44381a88357cd0f28d7aeed9 100644
--- a/src/ports/SkFontHost_win_dw.cpp
+++ b/src/ports/SkFontHost_win_dw.cpp
@@ -874,6 +874,11 @@ void SkScalerContext_DW::generateFontMetrics(SkPaint::FontMetrics* mx,
         mx->fBottom = mx->fDescent;
         mx->fLeading = fRec.fTextSize * SkIntToScalar(dwfm.lineGap) / upem;
         mx->fXHeight = fRec.fTextSize * SkIntToScalar(dwfm.xHeight) / upem;
+        mx->fUnderlineThickness = fRec.fTextSize * SkIntToScalar(dwfm.underlinePosition) / upem;
+        mx->fUnderlinePosition = fRec.fTextSize * SkIntToScalar(dwfm.underlineThickness) / upem;
+
+        mx->setFontMetricsFlag(SkPaint::FontMetrics::kUnderlineThinknessIsValid_FontMetricFlag);
+        mx->setFontMetricsFlag(SkPaint::FontMetrics::kUnderlinePositionIsValid_FontMetricsflag);
     }
 
     if (my) {
@@ -883,6 +888,11 @@ void SkScalerContext_DW::generateFontMetrics(SkPaint::FontMetrics* mx,
         my->fBottom = my->fDescent;
         my->fLeading = fRec.fTextSize * SkIntToScalar(dwfm.lineGap) / upem;
         my->fXHeight = fRec.fTextSize * SkIntToScalar(dwfm.xHeight) / upem;
+        my->fUnderlineThickness = fRec.fTextSize * SkIntToScalar(dwfm.underlinePosition) / upem;
+        my->fUnderlinePosition = fRec.fTextSize * SkIntToScalar(dwfm.underlineThickness) / upem;
+
+        my->setFontMetricsFlag(SkPaint::FontMetrics::kUnderlineThinknessIsValid_FontMetricFlag);
+        my->setFontMetricsFlag(SkPaint::FontMetrics::kUnderlinePositionIsValid_FontMetricsflag);
     }
 }