Collapse_text icon is missing in the ckeditor

Problem/Motivation

Collapse_text Button is not displaying in the ckeditor (admin/config/content/formats -> basic or full html editor)

Steps to reproduce

Enable Filter module
Enable Collpase_text module
Go to admin/config/content/formats
Edit Basic HTML editor
collapse_text Icon is missing

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes