RFR(xs): 8198269: Allow GCCauseSetter to be used outside of safepoints

[Per Liden]

Thanks Stefan and Stefan :)

/Per

On 02/19/2018 01:34 PM, Stefan Karlsson wrote:
> Looks good.
> 
> StefanK
> 
> On 2018-02-16 14:46, Per Liden wrote:
>> Patch to remove two overly aggressive asserts, to allow a GC to 
>> register the cause outside of a safepoint. Concurrent GC's (like ZGC) 
>> typically want to do this.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8198269
>> Webrev: http://cr.openjdk.java.net/~pliden/8198269/webrev.0/
>>
>> /Per