RFR: 8200429: Adjust object pinning interface on CollectedHeap

[Roman Kennke]

Am 03.04.2018 um 08:42 schrieb Per Liden:
> The recent additions to CollectedHeap to support object pinning didn't
> quite fit the bill for what the Shenandoah folks had in mind. Instead of
> having CollectedHeap::pin_obejct/unpin_object grab/release the GCLocker
> when object pinning is not supported, we add a
> CollectedHeap::supports_obejct_pinning() and let the caller take the
> appropriate action based on the response.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8200429
> Webrev: http://cr.openjdk.java.net/~pliden/8200429/webrev.0
> 
> /Per

Looks good to me. Thank you!

Roman