2439 [PP] Links are not underlined correctly

gfx/src/mac/nsFontMetricsMac.cpp

@@ -195,8 +195,8 @@ nsFontMetricsMac :: GetUnderline(nscoord& aOffset, nscoord& aSize)
 {
   float  dev2app;
   mContext->GetDevUnitsToAppUnits(dev2app);
-  aOffset = - dev2app;
-  aSize   = dev2app;
+  aOffset = -NSToCoordRound( dev2app );
+  aSize   = NSToCoordRound( dev2app );
   return NS_OK;
 }