STR:

1. open Preferences > Privacy & Security
2. scroll to the permission section
3. press on of the "Settings…" buttons

The font size of the whole dialog is too small. It's a regression from bug 1585482.

17:56.35 INFO: Narrowed inbound regression window from [1fb1ca98, e183cbb4] (3 builds) to [88b25807, e183cbb4] (2 builds) (~1 steps left)
17:56.35 INFO: No more inbound revisions, bisection finished.
17:56.35 INFO: Last good revision: 88b25807638231dcf403d8f0b597fc770f1d24a4
17:56.35 INFO: First bad revision: e183cbb4983cfb3aecf97ab18fad916b91f89e7e
17:56.35 INFO: Pushlog:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=88b25807638231dcf403d8f0b597fc770f1d24a4&tochange=e183cbb4983cfb3aecf97ab18fad916b91f89e7e

I performed the STR on a current version of Nightly and again on a pre-Bug 1585482 version of Nightly, and they look identical to me. Could you provide more information on your configuration? I think some of the font sizes are set to be specific to the Operating System. A screenshot might be nice too, if you wouldn't mind.

I attached a screenshot for comparison.
The operating system is macOS Catalina.

I have identified that this problem does not just happen on this page. It happens on any preferences dialog that does not actually use the <dialog> element, as a result of this change. Here are a list of dialogs that I believe have the same problem:

• https://searchfox.org/mozilla-central/source/browser/components/preferences/blocklists.xhtml
• https://searchfox.org/mozilla-central/source/browser/components/preferences/clearSiteData.xhtml
• https://searchfox.org/mozilla-central/source/browser/components/preferences/connection.xhtml
• https://searchfox.org/mozilla-central/source/browser/components/preferences/permissions.xhtml
• https://searchfox.org/mozilla-central/source/browser/components/preferences/siteDataSettings.xhtml
• https://searchfox.org/mozilla-central/source/browser/components/preferences/sitePermissions.xhtml
• https://searchfox.org/mozilla-central/source/browser/components/preferences/translation.xhtml

I'm looking into possible fixes for this. I haven't yet identified an obvious way of distinguishing, in CSS, the difference between a <window> with and without a <dialog> in it.

(In reply to Kirk Steuber (he/him) [:bytesized] from comment #3)

I have identified that this problem does not just happen on this page. It happens on any preferences dialog that does not actually use the <dialog> element, as a result of this change. Here are a list of dialogs that I believe have the same problem:

• https://searchfox.org/mozilla-central/source/browser/components/preferences/blocklists.xhtml
• https://searchfox.org/mozilla-central/source/browser/components/preferences/clearSiteData.xhtml
• https://searchfox.org/mozilla-central/source/browser/components/preferences/connection.xhtml
• https://searchfox.org/mozilla-central/source/browser/components/preferences/permissions.xhtml
• https://searchfox.org/mozilla-central/source/browser/components/preferences/siteDataSettings.xhtml
• https://searchfox.org/mozilla-central/source/browser/components/preferences/sitePermissions.xhtml
• https://searchfox.org/mozilla-central/source/browser/components/preferences/translation.xhtml

I'm looking into possible fixes for this. I haven't yet identified an obvious way of distinguishing, in CSS, the difference between a <window> with and without a <dialog> in it.

Is it possible we could switch that selector back to :root > *?

That seems like a reasonable solution to me. I'll post a patch.

https://hg.mozilla.org/mozilla-central/rev/3c214336a3b2