How to turn on/off $log.debug in AngularJS

I'm trying to use $log.debug("Foo"). How can it be turned on off. I can't find a sample anywhere. I think it need to be set in the config, but I cant seem to get that to work either.

Where does one set the on and off switch?

$logProvider.debugEnabled(true)

This is only available in AngularJs 1.1.2 or later.

https://github.com/angular/angular.js/pull/1625

Here is an example of it being set.

var app = angular.module('plunker', []);

app.config(function($logProvider){
  $logProvider.debugEnabled(true);
});

app.controller('MainCtrl', function($scope, $log ) {
  $scope.name = 'World';
  $scope.model = {value: "test"};
  $log.debug('TEST Log');
});

http://plnkr.co/edit/HZCAoS?p=preview

By default it is on.