Directory name matching https://w3c.github.io/device-memory/.

Change-Id: If32f07b659aca91a63fd17ca80de4afb1cd525c2
Reviewed-on: https://chromium-review.googlesource.com/876423
Reviewed-by: Fadi Meawad <[email protected]>
Reviewed-by: Shubhie Panicker <[email protected]>
Commit-Queue: Philip Jägenstedt <[email protected]>
Cr-Commit-Position: refs/heads/master@{#530859}