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I noticed one case in the README.md and figured that I should fix them
all.

Change-Id: I7c48a7a178ed377073c8e49a1884c961e8075053
Reviewed-on: https://chromium-review.googlesource.com/872194
Commit-Queue: Adam Langley <agl@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532291}