Convert visitedlink component to new shared memory API

This includes moving mojom shared_buffer usage to the more
strongly-typed base memory region types.

Bug: 826213
Change-Id: Ifb304267dc0c5a18a7a9df204b2b70020337b4e9
Reviewed-on: https://chromium-review.googlesource.com/985420
Reviewed-by: Tom Sepez <[email protected]>
Reviewed-by: Scott Violet <[email protected]>
Commit-Queue: Ken Rockot <[email protected]>
Cr-Commit-Position: refs/heads/master@{#547186}
10 files changed