RFR (S): 8213439: Run class initialization for boot loader classes with registered subgraph archiving entry field during CDS dump time

[Jiangli Zhou]

Please review following webrev that explicitly runs class initialization 
for classes (for boot loader only) with registered subgraph archiving 
entry field(s) during CDS dump time.

At CDS dump time, some of the loaded classes are initialized due to 
execution of java code. Currently there are 279 classes are initialized 
at dump time. The rest of the loaded classes are not initialized. 
Running class initialization for the boot classes with registered 
subgraph archiving entry field(s) will allow those static fields (and 
their directly/indirectly referenced objects) being populated at CDS 
dump time and archived. The Long$LongCache (planned for JDK-8213033 by 
Claes, thanks!) is such an example.

   webrev: http://cr.openjdk.java.net/~jiangli/8213439/webrev.00/

   RFE: https://bugs.openjdk.java.net/browse/JDK-8213439

The initialization of a class is triggered explicitly when processing 
the subgraph entry fields at dump time. For any class that's already 
initialized at this point, it's essentially a nop. That's the case for 
current existing subgraph entries.

Tested with tier1-tier3. Thanks David and Ioi's for discussions in the 
bug report.

Thanks,

Jiangli