Read through some of the Iron articles on this page. Especially the Iron vs Chrome. http://www.srware.net/en/software_srware_iron.php
IIRC, the Iron folks only remove things from the chromium source code that are very invasive as far as security and privacy go.
(GoogleSharing may fall into that category. If so, you may as well use Chrome as it is already invasive).
I don't think it is the Iron coders intention to ' add features'.
Have you looked for a comparable Chrome extension that duplicates the Firefox version?