RFR: JDK-8068243 - Expected IllegalArgumentException was not thrown

[alexey mironov]

issue: https://bugs.openjdk.java.net/browse/JDK-8068243
webrev: http://cr.openjdk.java.net/~amironov/8068243/

Please review the changes made in order to add IllegalArgumentException 
throwing in UARTEvent constructor.

Regards,
Alexey