RFR: 8213942:URLStreamHandler initialization race

[Pavel Rappo]

This fix assumes handlers returned from defaultFactory are interchangeable and that defaultFactory is thread-safe. If these assumptions are valid, looks good to me.

> On 21 Nov 2018, at 14:31, Chris Hegarty <chris.hegarty at oracle.com> wrote:
> 
> 
>> On 21/11/18 13:04, Seán Coffey wrote:
>> Thanks to all for the feedback. It makes sense to reduce the scope of the lock where possible.
>> I've updated the webrev :
>> http://cr.openjdk.java.net/~coffeys/webrev.8213942.v2/webrev/
> 
> Thanks Sean, this looks good.
> 
> -Chris.