chore: cherry-pick 9aa4c45f21b1 from chromium

[ppontes]

[M108-LTS] Shutdown RtpContributingSourceCache in Dispose().

The cache is an off-heap object, but it is owned by an on-heap object
(RTCPeerConnection). Dispoing the owning object poisons memory owned by
it, but the cache may have in-flight tasks (cache doing ClearCache in a
delayed microtask). This CL adds a Shutdown() method to ensure the
cache isn't doing anything in the next microtask after disposal.

No reliable way to repro this has been found but the change should be
safe so hoping we can land without tests.

(cherry picked from commit 4d450ecd6ec7776c7505dcf7d2f04157ff3ba0eb)

Bug: 1413628
Change-Id: I479aace9859f4c10cd75d4aa5a34808b4726299d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4247023
Commit-Queue: Henrik Boström hbos@chromium.org
Cr-Original-Commit-Position: refs/heads/main@{#1105653}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4291513
Reviewed-by: Achuith Bhandarkar achuith@chromium.org
Owners-Override: Achuith Bhandarkar achuith@chromium.org
Reviewed-by: Henrik Boström hbos@chromium.org
Commit-Queue: Zakhar Voit voit@google.com
Cr-Commit-Position: refs/branch-heads/5359@{#1404}
Cr-Branched-From: 27d3765d341b09369006d030f83f582a29eb57ae-refs/heads/main@{#1058933}

Ref electron/security#293

Notes: Security: backported fix for CVE-2023-1218.

[release-clerk]

Release Notes Persisted

Security: backported fix for CVE-2023-1218.