RFR: 8061431: [TESTBUG] closed/runtime/AppCDS/SharedArchiveConsistency.java fails on all platforms

[Yumin Qi]

Please review

bug: https://bugs.openjdk.java.net/browse/JDK-8061431
webrev: http://cr.openjdk.java.net/~minqi/8061431/webrev00/

Summary: The test failed since the variable offsets changed in hotspot. 
The way to get offset in test is hard-coded. To reduce the risk of 
future changes of hotspot offsets, the fix add a WhiteBox API function 
to get a map for FileMapHeaderInfo, which return the members' offsets in 
a Hashtable.  The test case in closed workspace, will post webrev for it 
internally.

Thanks
Yumin