network error: Add infrastructure to clear easter egg high score

Adds mojo + JS infrastructure to clear the dino game high score.
UI to be added by edwardjung@ later.

Bug: 568093, 911040
Change-Id: If9fc99a3fe3b262c4e4671b3a534b6726d6dcd3e
Reviewed-on: https://chromium-review.googlesource.com/c/1358501
Commit-Queue: Eric Seckler <eseckler@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613546}
8 files changed