review request (XXS) - 8060467: small OldPLABSize causes assert

[John Coomes]

Hi all,

Please review this small fix for

	8060467: CMS: small OldPLABSize and -XX:-ResizePLAB cause
		assert(ResizePLAB || n_blks == OldPLABSize) failed: Error

http://cr.openjdk.java.net/~jcoomes/9/8060467-cms-plab-assert/

-John