function runHandlers(handlerEvent, event) {
    var handler;
    for (var name in HANDLERS) {
      handler = HANDLERS[name];
      if (handler instanceof $$MdGestureHandler) {

        if (handlerEvent === 'start') {
          // Run cancel to reset any handlers' state
          handler.cancel();
        }
        handler[handlerEvent](event, pointer);
      }
    }
  }
When a DOM event happens, run all registered gesture handlers' lifecycle
methods which match the DOM event.
Eg. when a 'touchstart' event happens, runHandlers('start') will call and
run `handler.cancel()` and `handler.start()` on all registered handlers.