It looks like this: https://imgur.com/D6eNou4l.png And is 100% reproducible for me, even on a clean profile and on different versions of Firefox (50, 51, compiled from ports, installed as a pkg). On about:preferences (and about:addons) pages I am getting such a message in the Error Console: SDK worker-child started as frozen on unexpected initial document.readyState Object { initialDocumentReadyState: "uninitialized", windowLocation: "about:preferences" } worker-child.js:62 [ view-source:resource://gre/modules/commonjs/sdk/content/worker-child.js ]
Created attachment 184216 [details] ff56 (photon) Will be fixed upstream in Firefox 56 but the patch cleanly applies against Firefox 55 as well.
A commit references this bug: Author: jbeich Date: Mon Aug 7 18:22:52 UTC 2017 New revision: 447501 URL: https://svnweb.freebsd.org/changeset/ports/447501 Log: www/firefox: update to 55.0 This is the last release to support RUST=off. Later versions remove non-Rust codepaths e.g., via encoding_rs. Changes: https://www.mozilla.org/firefox/55.0/releasenotes/ PR: 216541 219963 Security: 555b244e-6b20-4546-851f-d8eb7d6c1ffa MFH: 2017Q3 Changes: head/Mk/Uses/gecko.mk head/www/firefox/Makefile head/www/firefox/distinfo head/www/firefox/files/patch-bug1021761 head/www/firefox/files/patch-bug1312182 head/www/firefox/files/patch-bug1356709 head/www/firefox/files/patch-bug1357874 head/www/firefox/files/patch-bug1360321 head/www/firefox/files/patch-bug1376411 head/www/firefox/files/patch-bug1385597 head/www/firefox/files/patch-bug702179 head/www/firefox/files/patch-bug826985 head/www/firefox/files/patch-bug847568 head/www/firefox/files/patch-bug981348 head/www/firefox/files/patch-python_futures_concurrent_futures_process.py head/www/firefox/files/patch-rust-option head/www/firefox/files/patch-third__party_python_futures_concurrent_futures_process.py head/www/firefox-i18n/Makefile head/www/firefox-i18n/Makefile.lang head/www/firefox-i18n/Makefile.option head/www/firefox-i18n/distinfo
Our FF55 update contains the fix as www/firefox/files/patch-bug1312182.
A commit references this bug: Author: jbeich Date: Thu Aug 10 15:36:57 UTC 2017 New revision: 447690 URL: https://svnweb.freebsd.org/changeset/ports/447690 Log: MFH: r447501 r447660 www/firefox: update to 55.0.1 This is the last release to support RUST=off. Later versions remove non-Rust codepaths e.g., via encoding_rs. Changes: https://www.mozilla.org/firefox/55.0.1/releasenotes/ PR: 216541 219963 Security: 555b244e-6b20-4546-851f-d8eb7d6c1ffa Approved by: ports-secteam (zi) Changes: _U branches/2017Q3/ branches/2017Q3/Mk/Uses/gecko.mk branches/2017Q3/www/firefox/Makefile branches/2017Q3/www/firefox/distinfo branches/2017Q3/www/firefox/files/patch-bug1021761 branches/2017Q3/www/firefox/files/patch-bug1312182 branches/2017Q3/www/firefox/files/patch-bug1356709 branches/2017Q3/www/firefox/files/patch-bug1357874 branches/2017Q3/www/firefox/files/patch-bug1360321 branches/2017Q3/www/firefox/files/patch-bug1376411 branches/2017Q3/www/firefox/files/patch-bug1385597 branches/2017Q3/www/firefox/files/patch-bug702179 branches/2017Q3/www/firefox/files/patch-bug826985 branches/2017Q3/www/firefox/files/patch-bug847568 branches/2017Q3/www/firefox/files/patch-bug981348 branches/2017Q3/www/firefox/files/patch-python_futures_concurrent_futures_process.py branches/2017Q3/www/firefox/files/patch-rust-option branches/2017Q3/www/firefox/files/patch-third__party_python_futures_concurrent_futures_process.py branches/2017Q3/www/firefox-i18n/Makefile branches/2017Q3/www/firefox-i18n/Makefile.lang branches/2017Q3/www/firefox-i18n/Makefile.option branches/2017Q3/www/firefox-i18n/distinfo