Fix incorrect em unit calculation in CssBoxProperties

Author: chenjt2001

Source/HtmlRenderer/Core/Dom/CssBoxProperties.cs

@@ -1432,14 +1432,14 @@ public double ActualBorderSpacingVertical
         /// <returns></returns>
         public double GetEmHeight()
         {
-            return ActualFont.Height;
+            return ActualFont.Size * 96d / 72d;
         }
 
-        /// <summary>
-        /// Ensures that the specified length is converted to pixels if necessary
-        /// </summary>
-        /// <param name="length"></param>
-        protected string NoEms(string length)
+		/// <summary>
+		/// Ensures that the specified length is converted to pixels if necessary
+		/// </summary>
+		/// <param name="length"></param>
+		protected string NoEms(string length)
         {
             var len = new CssLength(length);
             if (len.Unit == CssUnit.Ems)