about:rights uses two DTD files, aboutRights.dtd and security.dtd. security.dtd is not referenced from any other file.

Both of these file should be migrated to Fluent, and the string from security.dtd can be moved to aboutRights.ftl since it is not referenced from anywhere else.

Please note that aboutRights.dtd is referenced by Android build files and the patch will need to update those files accordingly.

Yuan is struggling here because, despite converting everything, fluent is not running so the page just looks empty.

This is because of the security checks at https://searchfox.org/mozilla-central/rev/330daedbeac2bba296d663668e0e0cf248bc6823/dom/base/Document.cpp#2032-2057 that will only allow fluent to run on pages that the web can't link to, or that are UI resources. about:rights is linkable by web content (see bug 1308351), and not marked as a UI resource, so we don't run fluent.

I'll file a dep bug to fix the web-linkability of about:rights now that about:home and about:newtab aren't web-linkable anymore. The only other about: pages that would then not be localizable would be about:logo (which is just a png), about:blank, about:srcdoc (both web-modifiable, so that's correct) and about:license, which doesn't have localizable content ( https://searchfox.org/mozilla-central/source/toolkit/content/license.html ) so hopefully that will be all...

https://hg.mozilla.org/mozilla-central/rev/75766cc3befd