RFR: 8153749 - New capability can_generate_early_class_hook_events

[serguei.spitsyn at oracle.com]

Please, review the Jigsaw-related fix for:
   https://bugs.openjdk.java.net/browse/JDK-8153749


Hotspot webrev:
http://cr.openjdk.java.net/~sspitsyn/webrevs/2016/hotspot/8153749-Jigsaw-newcap.hs1/

Jdk webrev:
http://cr.openjdk.java.net/~sspitsyn/webrevs/2016/jdk/8153749-Jigsaw-newcap.jdk1/


Summary:

    This is a Jigsaw related enhancement.
    Some agents need to get a CFLH event for classes loaded in the 
primordial phase.
    This is not possible in JDK 9 because existing agents may instrument 
code in the
    primordial or start phase before the module system has completed 
initialization.

    We introduce a new capability: can_generate_early_class_hook_events.
    If this capability and can_generate_all_class_hook_events are 
enabled then
    the CFLH event could be posted for classes loaded in the primordial 
phase.
    We leave can_generate_early_vmstart as is, no changes.

    This enhancement needs a CCC request filed.
    I will file it once the JVMTI spec changes are reviewed.


Testing:
    Altered the nsk.jvmti co-located test 
nsk/jvmti/ClassFileLoadHook/classfloadhk002
    to enable the can_generate_early_class_hook_events and checked that 
new CFLH events
    are posted in the primordial phase and also they are not posted 
otherwise.


Thanks,
Serguei