jenkinsci/jenkins — pull request #396 by ohtake (2012-03-02 06:55:31+00:00)
Title: Prototype.js: Ajax parameters option should not be a raw string

http://www.prototypejs.org/api/ajax/options

> This can be provided either as a URL-encoded string or as any Hash-compatible object (basically anything), with properties representing parameters.

Prototype 1.5.1.1 encodes parameters, but 1.7.0 does not. If Jenkins uses 1.7.0, he warns us of container's encoding regardless of container's configuration.