/usr/lib/thunderbird-addons/extensions/ is in xul-ext-gdata-provider 1:52.7.0+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
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/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/browserRequest.js
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider/content/browserRequest.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-creation.js
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/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider/content/gdata-calendar-event-dialog.js
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/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider/content/gdata-calendar-properties.js
/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider/content/gdata-calendar-properties.xul
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/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider/content/gdata-migration-overlay.xul
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/usr/lib/thunderbird-addons/extensions/{a62ef8ec-5fdc-40c2-873c-223b8a6925cc}/chrome/gdata-provider/skin//
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