RFR(M) 8176100: [REDO][REDO] G1 Needs pre barrier on dereference of weak JNI handles

[Kim Barrett]

> On Mar 14, 2017, at 9:11 AM, Mikael Gerdin <mikael.gerdin at oracle.com> wrote:
> 
> Here we go again...
> This time around the fix is exactly the same but since I changed the lock ranks in 8176363 we shouldn't be hitting any lock ordering assertions.
> 
> 
> […]
> Full webrev:
> http://cr.openjdk.java.net/~mgerdin/8176100/webrev.0/
> 
> Bugs:
> https://bugs.openjdk.java.net/browse/JDK-8176100
> https://bugs.openjdk.java.net/browse/JDK-8175085
> https://bugs.openjdk.java.net/browse/JDK-8166188
> 
> Thanks
> /Mikael

Looks good.  But I've said that before. Hopefully we've run out of
places that cheat about the "equivalence" of jobject and oop*.