Revert 232837 "Linux: add a Credentials class to handle Linux ca..."

> Linux: add a Credentials class to handle Linux capabilities.
> 
> (This is a re-land of https://chromiumcodereview.appspot.com/51113009/)
> 
> BUG=312380
> TBR=jorgelo@chromium.org
> 
> Review URL: https://codereview.chromium.org/55603003

TBR=jln@chromium.org

Review URL: https://codereview.chromium.org/45923006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232842 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232842