I've just confirmed by visual inspection that mozilla-central and comm-central don't use treecol type="password".
Bug 1508165 Comment 3 Edit History
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I've just confirmed by visual inspection that mozilla-central and comm-central don't use treecol type="password". https://searchfox.org/comm-central/search?q=type%3D%22password%22&case=false®exp=false&path=.xul%24