RFR: 8214785: Remove unused WeakHandleType::vm_string

[Per Liden]

On 2018-12-04 16:47, coleen.phillimore at oracle.com wrote:
> Also looks good (and trivial).  I have this change in some private repo 
> of mine.

Thanks Coleen! Just happened to run across this so I thought I'd just 
fix it right away instead of bothering someone else ;)

/Per

> thanks,
> Coleen
> 
> On 12/4/18 8:03 AM, Per Liden wrote:
>> The enum WeakHandleType::vm_string is never used and can be removed. 
>> The StringTable uses WeakHandleType::vm_string_table_data.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8214785
>> Webrev: http://cr.openjdk.java.net/~pliden/8214785/webrev.0
>>
>> /Per
>