This removes the sychronous operation of the command buffers. It also
introduces a serial type for assigning ids to queue operations. This
gives us the ability to manage lifetimes of resources and track when
they're no longer in use on the device.

BUG=angleproject:1898

Change-Id: I91a4836d3098f1d7bd06cd389d88601a3a4826ab
Reviewed-on: https://chromium-review.googlesource.com/428352
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>