arrayBuffer() should leave the stream locked

[ricea]

For consistency with Response arrayBuffer(), IncomingStream arrayBuffer() should leave the stream locked after it has finished reading.

[vasilvv]

Discussed at the meeting today. The conclusion is that we should not implement arrayBuffer() in the IncomingStream, and instead make sure that there is a uniform way to do .arrayBuffer()/.text()/.json() on any readably stream. Currently, new Response(stream).arrayBuffer() is a way to do that, but it's unclear if it has same performance properties; if not, we should address that (on spec and/or implementation level as appropriate).

[jan-ivar]

Suggest postponing it until we have movement in the streams standard whatwg/streams#1019

[jan-ivar]

Consensus to remove the incomingStream.arrayBuffer()