Revert 233048 "Support policies referencing external data for de..."

The CL broke compilation on Chrome OS.

> Support policies referencing external data for device-local accounts
> 
> This CL adds a DeviceLocalAccountExternalDataService that provides each
> device-local account with a DeviceLocalAccountExternalDataManager which
> fetches, caches and retrieves external policy data.
> 
> BUG=256635
> TEST=New browser test
> R=derat@chromium.org, joaodasilva@chromium.org
> 
> Review URL: https://codereview.chromium.org/25242002

TBR=bartfab@chromium.org

Review URL: https://codereview.chromium.org/60683002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233051 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233051