Change record status: 
Project: 
Introduced in branch: 
8.x-1.x
Introduced in version: 
8.x-1.13
Description: 

Previously \Drupal\metatag\MetatagManager::generateRawElements discarded cacheability metadata resulting in performance issues.
From 8.x-1.13 it now collects it, which means the function expects a bubbleable metadata argument.
Calling the method without that argument will trigger a deprecation notice.