RFR JDK-8157273: Simplify outgoing messages queueing policy in WebSocket API

[Pavel Rappo]

> On 13 Jun 2016, at 12:14, Simone Bordet <simone.bordet at gmail.com> wrote:
> 
> Close should definitely *not* "jump ahead of the queue", it should be
> sent after queued stuff has been sent.

Why is that? Shouldn't we treat this as an implementation specific detail? I
mean Close, Ping and Pong are control messages. They are differ from Text and
Binary ones.

If we specify this straight away, we're closing the ability for Close to behave
like this. Are you sure this kind of Close behaviour is *never* needed?
Meanwhile it's easy to note in the API that if one wants to *force* order then
sendClose should be chained through CSs. It should be easy, especially taking
into account Close is the last message sent by a client.