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Nothing uses these on Mac.

They're used a lot on ChromeOS. On Windows, it shows a default browser
selection dialog. On Linux it shows the certificate viewer. On Mac I
think it was once used for a webui task manager.

BUG=None

Review URL: https://codereview.chromium.org/1640043002

Cr-Commit-Position: refs/heads/master@{#371971}