As an adopted library that does not follow the WordPress Coding Standards, the file ended with a mix of tab and spaces as part of maintenance updates over the years.
This commit standardizes on spaces for now, to bring some consistency while minimizing the number of changes.
Includes moving all the declared properties to the top of the class.
Follow-up to [11875], [11877], [23376], [32990], [46377], [54037].
See #55647.
Built from https://develop.svn.wordpress.org/trunk@54038
git-svn-id: http://core.svn.wordpress.org/trunk@53597 1a063a9b-81f0-0310-95a4-ce76da25c4cd