RFR: JDK-8078904 : CMS: Assert failed: Ctl pt invariant

[Eric Caspole]

Thomas and I had a IM about this the other day and in the end decided to 
allow the main rescan chunk array to grow if the user explicitly sets a 
very small MinTLABSize on the command line. There doesn't seem to be any 
good reason to set a very small MinTLABSize except maybe stress testing, 
and so it is simpler to grow this structure for that unusual case rather 
than use the stride I had in v03.

The new one is here:

  http://cr.openjdk.java.net/~ecaspole/JDK-8078904/04/webrev/

Bug:
  https://bugs.openjdk.java.net/browse/JDK-8078904

I tested this with the failing example using many combinations of gc
thread counts and many MinTLABSize values from 64 up to 4M. And JPRT.
Thanks,
Eric