chore: cherry-pick da11d71a0227 from chromium

[ppontes]

mojo/ipc: Drop messages targeting invalid task runner

If the endpoint's task runner does not match the current task runner (or
an equivalent main-thread task runner for the ChannelProxy) when a
executing a message dispatch task for that endpoint, this ignores the
message instead of dispatching it on the wrong sequence.

(cherry picked from commit 0747c9405e1098c0bbbc5593183696eafb45b72c)

Fixed: 1263457
Change-Id: I4f6ba22de3ff8cf3994b748e1ffd0f0aabb17b70
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3318601
Reviewed-by: Daniel Cheng dcheng@chromium.org
Commit-Queue: Ken Rockot rockot@google.com
Cr-Original-Commit-Position: refs/heads/main@{#949140}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3328403
Auto-Submit: Ken Rockot rockot@google.com
Commit-Queue: Daniel Cheng dcheng@chromium.org
Cr-Commit-Position: refs/branch-heads/4664@{#1269}
Cr-Branched-From: 24dc4ee75e01a29d390d43c9c264372a169273a7-refs/heads/main@{#929512}

Notes: Backported fix for CVE-2021-4098.

[release-clerk]

Release Notes Persisted

Backported fix for CVE-2021-4098.