message: Fixed back handler removal
diff: @@ -8,11 +8,11 @@ var createBackHandler = () => {
  var addEventListener = (eventName, handler) => {
  if (listeners.indexOf(handler) === -1)
  listeners.push(handler);
  - return { remove: removeEventListener(eventName, handler) };
  + return { remove: () => removeEventListener(eventName, handler) };
  }
  var removeEventListener = (_, handler) => {
  if (listeners.indexOf(handler) !== -1)
  - listeners.slice(listeners.indexOf(handler));
  + listeners.splice(listeners.indexOf(handler));
  }
  return {listeners, addEventListener, removeEventListener};
  }
  