function $BrowserProvider() {
  this.$get = ['$window', '$log', '$sniffer', '$document',
      function($window, $log, $sniffer, $document) {
        return new Browser($window, $document, $log, $sniffer);
      }];
}
@name $browser#defer.cancel

@description
Cancels a deferred task identified with `deferId`.

@param {*} deferId Token returned by the `$browser.defer` function.
@returns {boolean} Returns `true` if the task hasn't executed yet and was successfully
                   canceled.