Here is an example of the upcoming release of analysis-core: Priority Doughnut Graph. If I change the graph type to a bar-chart then the error in the stack trace (comment before) appears.
The fix has been integrated towards 2.110. I am not marking it as LTS candidate, because it seems to be a bit risky to backport it. Ulli Hafner please mark it as LTS candidate if you need it in the release
This issue caught my eye, when I was trying to solve the Jenkins slow loading problem reported in JENKINS-56243. After upgrading to Jenkins 2.181 loading was fast again, but for some multibranch projects loading a branch seemd to load completely, but hang in there for 30+ seconds and it seems prototype.js was the culprit that did not quite finish.
There is no fix yet, so no chance to get it into the LTS release. The fix above (https://github.com/jenkinsci/jenkins/pull/3277) has been reverted since several old plugins rely on the old and broken prototype functionality. Since we have no UI tests for them (and no responsible UI architect in core) I doubt that we ever get rid of this library.