hg: jdk9/hs-gc: 8043225: Make whitebox API functions more stable

[igor.ignatyev at oracle.com]

Changeset: e36425f51dff
Author:    iignatyev
Date:      2015-04-02 19:09 +0300
URL:       http://hg.openjdk.java.net/jdk9/hs-gc/rev/e36425f51dff

8043225: Make whitebox API functions more stable
Summary: Added checks for null parameters where applicable
Reviewed-by: dholmes, iignatyev
Contributed-by: Kirill Zhaldybin <kirill.zhaldybin at oracle.com>

! test/lib/sun/hotspot/WhiteBox.java