RFR(S): Handle Java heap initialization and expansion failure

[Zhengyu Gu]

Java heap initialization and expansion may not always success.

Fail to initialize Java heap should result JVM to exit with OOM error, 
and fail to expand Java heap should not result fatal crash.

Webrev: 
http://cr.openjdk.java.net/~zgu/shenandoah/handle_heap_expansion_failure/webrev.00/


Thanks,

-Zhengyu