[16] RFR 8251192: Shenandoah: Shenandoah build failed after JDK-8235573

[Zhengyu Gu]

Please review this small patch that fixes build failure with Shenandoah.

Bug: https://bugs.openjdk.java.net/browse/JDK-8251192
Webrev: http://cr.openjdk.java.net/~zgu/JDK-8251192/webrev.00/

Test:
   Built on Linux x86_84

Thanks,

-Zhengyu