Revert "InMemory MediaCapabilities DB for Guest/Incognito profiles"

This reverts commit e34efffbfefec5d70b39bcbda16a5806fa4bf7c4.

Reason for revert: see bug 855215

Original change's description:
> InMemory MediaCapabilities DB for Guest/Incognito profiles
>
> Prior to this change, Guest mode has an empty read-only DB and Incongito
> has a read-only DB. This CL allows both profiles to write to an "in
> memory" database that disapears when the profile is destroyed.
>
> This improves the experience for the user and avoids the possibility
> of using MediaCapabilites to detect incognito/guest profiles.
>
> R=​jam@chromium.org
>
> Bug: 796280
> Change-Id: I37e25478ce6efe8c25bf49f77929f94c9ca27655
> Reviewed-on: https://chromium-review.googlesource.com/1092156
> Reviewed-by: John Abd-El-Malek <jam@chromium.org>
> Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
> Reviewed-by: Scott Violet <sky@chromium.org>
> Commit-Queue: Chrome Cunningham <chcunningham@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#569046}

TBR=sky@chromium.org,jam@chromium.org,mlamouri@chromium.org,chcunningham@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 796280
Change-Id: Idc97eee2871e940e36b9c19f820d9f6207d7f6ef
No-Try: True
Reviewed-on: https://chromium-review.googlesource.com/1113958
Commit-Queue: Mounir Lamouri <mlamouri@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#570199}(cherry picked from commit 80a416c8129c930347eaaa7e571fd8af6b7487db)
Reviewed-on: https://chromium-review.googlesource.com/1113844
Cr-Commit-Position: refs/branch-heads/3472@{#4}
Cr-Branched-From: 3816ddd3a9aa8a35aaff936186a6ac7e0ecf18da-refs/heads/master@{#569948}
17 files changed