Code review comment for lp:~vanvugt/mir/schedule-nonblocking

The IPC _is_ happening on the IPC thread, but that is still indirectly blocking the compositor thread due to poor mutex management...

We just have a dumb ordering of operations right now:
.. 1. Received new buffer
.. 2. Lock the Stream lock (which hangs the compositor if it is trying to redraw).
.. 3. Queue the new buffer for compositing.
** 4. Send dropped buffer back to the client (blocking socket IO).
.. 5. Unlock the Stream lock so the compositor won't hang.
.. 6. Notify the compositor that the scene has changed and that it should start redrawing.

This branch changes the order of operations:
.. 1. Received new buffer
.. 2. Lock the Stream lock (which hangs the compositor if it is trying to redraw).
.. 3. Queue the new buffer for compositing.
.. 4. Unlock the Stream lock so the compositor won't hang.
.. 5. Notify the compositor that the scene has changed and that it should start redrawing.
** 6. Send dropped buffer back to the client (blocking socket IO).