GitLab

Moves the XrConsentHelper and XrConsentPromptLevel interfaces to
content/public and moves the windows-specific implementation out of
chrome/browser/vr/service. Creates a wrapper method for the windows-
specific singleton to better fit the pattern of the other consent
helpers.

Note that the XrConsentHelpers are currently disabled by default and
intended to be removed once the switch to use permissions has shipped,
but due to the current release changes, this is looking further out.
Thus, these methods are moved temporarily to enable VRService to move.

Bug: 1031622
Change-Id: I54b0ee16d27e0cf95dbe562e064e0f24b7ac30e4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2118579
Commit-Queue: Alexander Cooper <alcooper@chromium.org>
Reviewed-by: Klaus Weidner <klausw@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#753344}