Update ManagedUserService tests to create the service using ManagedUserServiceFactory

Using ManagedUserServiceFactory to create the service instead of directly constructing the service allow for correct shutdown (Shutdown method to be called)

To prevent this from happening again we:
1- We DCHECK that Shutdown method is called before destruction of ManagedUserService
2- We make the constructor of ManagedUserService accessible only to ManagedUserServiceFactory

BUG=None

Review URL: https://chromiumcodereview.appspot.com/18337013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@210677 0039d316-1c4b-4281-b951-d872f2087c98
3 files changed