Request for review: 8004132 SerialGC ValidateMarkSweep code broken

[Tao Mao]

8004132 : SerialGC: ValidateMarkSweep broken when running GCOld
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8004132

http://cr.openjdk.java.net/~tamao/8004132/webrev.00/

Passed JPRT; I checked ValidateMarkSweep can't be triggered now with the 
fix.

Background:

While verifying the functionality of the ValidateMarkSweep code with the 
Serial collector (prior to adding code to enable this feature in G1) Tao 
and myself saw various crashes and failures when running GC Old.

Script to run GCOld:
#JHOME=/export/jdk8/solaris-x64
#JHOME=/java/re/jdk/6/promoted/latest/binaries/solaris-i586/fastdebug
JHOME=/export/bugs/8001047/jdk7/solaris-x64

$JHOME/bin/java -server -Xms1g -Xmx1g \
         -XX:+UseSerialGC \
         -XX:+ValidateMarkSweep \
         -XX:+PrintGCDetails -XX:+PrintGCTimeStamps 
-XX:+ShowMessageBoxOnError \
                 GCOld 9000 20 5 30 500000

Note the ValidateMarkSweep functionality is only available in 
non-product builds.

This seems to have been broken for a long while - we even saw the crash 
with jdk6. Thus we suggest to remove the ValidateMarkSweep code.