A closer look at event_managers method for searching though its plugins to find valid eventplugins using the implemented supports() function.

event_manager_finding_plugins.ts

addEventListener(element: HTMLElement, eventName: string, handler: Function): Function {
    var plugin = this._findPluginFor(eventName);
    return plugin.addEventListener(element, eventName, handler);
  }

addGlobalEventListener(target: string, eventName: string, handler: Function): Function {
  var plugin = this._findPluginFor(eventName);
  return plugin.addGlobalEventListener(target, eventName, handler);
}

getZone(): NgZone { return this._zone; }

/** @internal */
_findPluginFor(eventName: string): EventManagerPlugin {
  var plugins = this._plugins;
  for (var i = 0; i < plugins.length; i++) {
    var plugin = plugins[i];
    if (plugin.supports(eventName)) {
      return plugin;
    }
  }
  throw new BaseException(`No event manager plugin found for event ${eventName}`);
}