RFR: 8202230: Provide accessors for JNIHandles storage objects

[Thomas Schatzl]

Hi,

On Wed, 2018-04-25 at 17:09 -0400, Kim Barrett wrote:
> Please review this addition to JNIHandles, providing access to the
> OopStorage objects used to manage the global and weak global handles.
> The accessors assert the storage objects have been allocated.
> 
> Also changed direct uses of the storage object variables to instead
> use the new accessors, to get the initialization asserts during
> development.
> 
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8202230
> 
> Webrev:
> http://cr.openjdk.java.net/~kbarrett/8202230/open.00/
> 
> Testing:
> {jdk,hs}-tier{1,2,3} for all Oracle platforms.
> 

  looks good.

Thomas