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

@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.