sendFrame() implemented in LOOLWebSocket is thread safe, and also deals with
large messages - sends the "nextmessage: size=..." frame before the actual
large frame.
The problem this is attempting to solve was that when sending a large frame,
it was split to multiple packets. During that, another frame was sent from a
different thread; which lead to confusion, and the resulting frame was
corrupted (because it ended up composed from unrelated packets).
Change-Id: Ie85952e431b1cad2fdc6e3c64df8a444ea0ae971