Hello,
In the AUI upgrade guide (AUI 8 upgrade guides - AUI Documentation), cookie is marked as a resource not anymore included in ajs and requiring an explicit web resource declaration.
However, based on our test and the dependency declared in the Jira HipChat Plugin, the given web resource key com.atlassian.auiplugin:aui-cookie looks to be the wrong one. It should be com.atlassian.auiplugin:cookie.
Documentation probably needs to be updated ?