/usr/lib/thunderbird-addons/extensions/ is in xul-ext-gdata-provider 1:24.4.0+build1-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome.manifest
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider-en-US//
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider-en-US/locale//
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider-en-US/locale/en-US//
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider-en-US/locale/en-US/gdata.dtd
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider-en-US/locale/en-US/gdata.properties
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider//
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider/content//
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider/content/calendarCreation.xul
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider/content/gcal.png
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider/content/gdata-calendar-event-dialog.xul
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider/content/gdata-event-dialog-reminder.xul
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider/content/gdata-migration-overlay.xul
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider/content/gdata-migration-wizard.xul
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider/content/gdata-migration.js
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider/skin//
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider/skin/gdata-event-dialog-reminder.css
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider/skin/reminder-action-sms.png
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/components/
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/components/calGoogleCalendarModule.js
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/components/calGoogleCalendarModule.manifest
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/components/gdata.xpt
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/components/interfaces.manifest
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/defaults/
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/defaults/preferences/
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/defaults/preferences/preferences.js
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/install.rdf
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/js/
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/js/calGoogleCalendar.js
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/js/calGoogleRequest.js
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/js/calGoogleSession.js
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/js/calGoogleUtils.js