Remove the MediaPermissionStatus helper class

Originally MediaPermissionStatus was added to facilitate moving some of
the permissions logic out of MediaStreamDevicesController. It turns out
that it is simpler to move the permission request logic out instead, as
is done in the followup CL: https://codereview.chromium.org/2811913002

This CL removes that helper class and moves the functionality back into
GetContentSetting.

BUG=596786

Review-Url: https://codereview.chromium.org/2810743004
Cr-Commit-Position: refs/heads/master@{#465111}
2 files changed