code: function instrument(name, _payload, callback, binding) {
        if (subscribers.length === 0) {
          return callback.call(binding);
        }
        var payload = _payload || {};
        var finalizer = _instrumentStart(name, function () {
          return payload;
        });
        if (finalizer) {
          var tryable = function _instrumenTryable() {
            return callback.call(binding);
          };
          var catchable = function _instrumentCatchable(e) {
            payload.exception = e;
          };
          return tryCatchFinally(tryable, catchable, finalizer);
        } else {
          return callback.call(binding);
        }
      }
docs: Notifies event's subscribers, calls `before` and `after` hooks.
  
  @method instrument
  @namespace Ember.Instrumentation
  
  @param {String} [name] Namespaced event name.
  @param {Object} payload
  @param {Function} callback Function that you're instrumenting.
  @param {Object} binding Context that instrument function is called with.