Re-enable QoS for UDPSocket under Windows.

 - Move QoSCreateHandle to a background task, letting critical socket operations continue unblocked while it executes.
 - Improve resetting handle when it returns REINITIALIZATION_NEEDED
 - Widen unit tests
 - Undo ifdef disabling QOS that was added because of hangs/stalls noted in bug 812137

Cq-Include-Trybots: luci.chromium.try:linux_mojo
Change-Id: I383955c2a218f23974a3f5e7044ae0464e99a43f
Bug: 812137, webrtc:5836
Reviewed-on: https://chromium-review.googlesource.com/c/1195936
Reviewed-by: Ryan Hamilton <rch@chromium.org>
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Commit-Queue: Tim Haloun <thaloun@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603269}
4 files changed