RFR: 8213942:URLStreamHandler initialization race

[Pavel Rappo]

> On 20 Nov 2018, at 17:55, Seán Coffey <sean.coffey at oracle.com> wrote:
> 
> Access to the handlers Hashtable and the factory should be made while holding the streamHandlerLock lock

I'm not sure about that. I wouldn't go with coarsening this lock's region. I
would rather go with an additional check for handler being null. It doesn't look
like this lock has ever had that big of a scope and bear in mind this place
might be very startup-time sensitive. So, in order to not steer clear of any
potential issues with that or deadlocks I would simply introduce an
unconditional null check.

-Pavel