Merge to M73: Revert "Use a separate socket for sending in mDNS code." and rebase.

This reverts commit affe2337daa2aa1852c8c0df5b399a7e717c6fa5. The
commit 8ce001913d238eef5fc09d30cd0abce5843972e4 is also reverted to
rebase.

Reason for revert: crbug.com/931916

TBR=msramek@chromium.org

Original change's description:
> Use a separate socket for sending in mDNS code.
>
> TBR=thestig@chromium.org
>
> Bug: 899310, 905422
> Change-Id: I5ea07adb3d3241af2f0056299bdd4b5b7b0d479a
> Reviewed-on: https://chromium-review.googlesource.com/c/1367366
> Commit-Queue: Qingsi Wang <qingsi@google.com>
> Reviewed-by: Eric Orth <ericorth@chromium.org>
> Reviewed-by: Martin Šrámek <msramek@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#625092}

(cherry picked from commit 5410ef0b210fee053a466bd91764d269d0d978ba)

Bug: 899310, 905422
Change-Id: I5bc329f417131dfdbabaa0d041fe9c47395da5e4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1498716
Commit-Queue: Qingsi Wang <qingsi@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Eric Orth <ericorth@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#637784}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1504700
Reviewed-by: Sean Kau <skau@chromium.org>
Cr-Commit-Position: refs/branch-heads/3683@{#761}
Cr-Branched-From: e51029943e0a38dd794b73caaf6373d5496ae783-refs/heads/master@{#625896}
13 files changed