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Also adds a test to verify the behavior.

BUG=957138
TEST=new base_unittest passes

Change-Id: Ida1d0801f457e96dbf1d2ed299966a50aec05442
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1586220
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654698}