Simplify TimeZoneInfo.Equals(object)

src/mscorlib/src/System/TimeZoneInfo.cs

@@ -946,11 +946,7 @@ static public DateTime ConvertTimeBySystemTimeZoneId(DateTime dateTime, String s
         }
 
         public override bool Equals(object obj) {
-            TimeZoneInfo tzi = obj as TimeZoneInfo;            
-            if (null == tzi) {
-                return false;
-            }            
-            return Equals(tzi);
+            return Equals(obj as TimeZoneInfo);
         }
 
         //