[15] RFR(T) 8243848: Shenandoah: Windows build fails after JDK-8239786

[Zhengyu Gu]

Please review this small patch that fixes build problems (size_t => uint 
type conversion) on Windows.


Bug: https://bugs.openjdk.java.net/browse/JDK-8243848
Webrev: http://cr.openjdk.java.net/~zgu/JDK-8243848/webrev.00/

Test:
   Built on Windows.

Thanks,

-Zhengyu