6627787: CMS: JVM refuses to start up with -Xms16m -Xmx16m
7000125: CMS: Anti-monotone young gen sizing with respect to maximum whole heap size specification
7027529: CMS: retire CMSUseOldDefaults flag
Summary: Simplify CMS heap sizing code, relying on ergonomic initial sizing consistent with other collectors for the most part, controlling only young gen sizing to rein in pause times. Make CMS young gen sizing default statically cpu-dependant. Remove inconsistencies wrt generation sizing and policy code, allowing for the fixing for 6627787 and 7000125. For 7027529, retire the flag CMSUseOldDefaults which had been introduced as a bridge from JDK 5 to JDK 6 a number of years ago.
Reviewed-by: brutisso, poonam