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... to assure DevTools protocol callbacks are always invoked (and destroyed) on the
correct thread.

Change-Id: Ie94c67d754138161ba22192bb76891f4021ad280
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1775501
Commit-Queue: Andrey Kosyakov <caseq@chromium.org>
Reviewed-by: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691793}