RFR: 8222664: runtime/appcds/sharedStrings/SharedStringsStress.java assert GC active during NoGCVerifier

[Per Liden]

Thanks for reviewing, Ioi!

/Per

On 4/24/19 7:23 AM, Ioi Lam wrote:
> Looks good. Thanks for fixing this.
> 
> - Ioi
> 
> On 4/23/19 12:55 AM, Per Liden wrote:
>> Deduplication of Strings must not happen when we're in a safepoint. 
>> However, during startup, we fail to block safepoint when calling 
>> deduplicate_shared_strings(), which sometimes results in hitting the 
>> NoSafepointVerifier assert.
>>
>> Testing: tier1-3
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8222664
>> Webrev: http://cr.openjdk.java.net/~pliden/8222664/webrev.0
>>
>> /Per
>