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 * Avoid allocating memory during logging.
 * Post logs to a lower-priority thread for actual output.

Bug: internal b/162244426
Change-Id: Iae080bcfebc96a151fed6f108cbfb12ff70a44ae
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2324819Reviewed-by: Yuchen Liu <yucliu@chromium.org>
Commit-Queue: Kenneth MacKay <kmackay@chromium.org>
Cr-Commit-Position: refs/heads/master@{#794783}