/**
* {@inheritdoc}
*
* Block configuration entities are a special case: one block entity stores
* the placement of one block in one theme. Changing these entities may affect
* any page that is rendered in a certain theme, even if the block doesn't
* appear there currently. Hence a block configuration entity must also return
* the associated theme's cache tag.
*/
public function getCacheTag()
{
return Cache::mergeTags(parent::getCacheTag(), ['theme:' . $this->theme]);
}
