RFR: Fixed two string dedup issues

[Aleksey Shipilev]

On 10/10/2017 03:47 PM, Zhengyu Gu wrote:
> Updated webrev: http://cr.openjdk.java.net/~zgu/shenandoah/strdedup_fix/webrev.01/index.html

This looks good to me.

Can you explain a little more why do we need to filter for only Shenandoah safepoints? The string
would only be queued, why does it matter if we are not in Shenandoah safepoint?

If it does matter, then I would expect ShenandoahStringDedup::enqueue_from_safepoint asserting the
Shenandoah-specific, not generic safepoint, right?

Thanks,
-Aleksey