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This is a cleaner/more general implementation and lets us remove the
one-off version the context manager uses.

Bug: b/175360169
Change-Id: I3356edc8b98d539476c686d624179cdfc7eaa906
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2603232
Commit-Queue: Nic Hollingum <hollingum@google.com>
Reviewed-by: Daniel Ng <danielng@google.com>
Cr-Commit-Position: refs/heads/master@{#839699}