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Today’s meeting leader is: emalysz

General Topics / Roundtable

  • [mconley] Using nsIDocShellTreeItem methods / properties is no longer desirable. These things will soon be gone. Please use BrowsingContext equivalents instead. Ask in Matrix:#fission if you need help.

Friends of the Firefox team


Resolved bugs (excluding employees)

Fixed more than one bug

  • Andrew Park
  • Itiel
  • kenrick95
  • Sonia

New contributors (🌟 = first patch)

Project Updates


Add-ons / Web Extensions

Addon Manager & about:addons

  • Share fixed a couple of issues that were preventing addons from being installed or updated when the builtin cert was not being used (which is the case for some organizations that use their own certificates, or because of some antivirus that install its own certificate to inspect HTTPS connections) - Bug 1647360 and Bug 1648815
  • Will Durand made sure that the sourceURL in the addon abuse reports submitted by users will be set to the expected source url even when the website did change it using the history API - Bug 1648036
  • Andrew Park contributed a fix that prevents the addon download doorhanger to show “NaN bytes/sec” when the download starts - Bug 1544570

WebExtensions Framework

  • Agi fixed a perf issue related to main thread I/O on startup when the rkv-based ExtensionPermissions backend is in use (only Nightly at the moment) - Bug 1651628 (main thread I/O originally introduced in Bug 1637680)
  • Landed an initial part of the changes needed to support Extension’s service workers and the manifest v3 background service workers (locked behind prefs “extensions.backgroundServiceWorker.enabled” and “extensions.service_worker_register.allowed”, currently both false by default on all channels) - Bug 1609920 (as a side note: even when enabled using the supported prefs no WebExtensions API are yet available in the Extension’s service workers)

WebExtension APIs

  • Rob fixed the validation of the chrome_settings_override’s search_url/suggest_url/search_form, which was allowing more than just localhost urls in those manifest properties - Bug 1651665 (landed in 80 and pending an uplift request to 79, where the originally regression landed, Bug 1612013)
  • Harsh Arora contributed a small fix to ensure that the API is going to log in the BrowserConsole unexpected errors raised internally when a download fails - Bug 1645337 (originally regressed by Bug 1576333)


Firefox Accounts

Sync and Storage

  • [read-only] Paused on migration users (we’re at 58% of total sync traffic now) until we resolve a Spanner hotspotting issue. Reviewing proposed mitigation with Google now and will proceed with internal QA after that.


  • [read-only] Possible fix for unreliable Send Tab on iOS issue found; in review now and will be deployed (likely) with the 7/28 release.

Developer Tools

  • Layout & Mobile Tools - Better support for XPath search. More expressions can be used - previously only expressions starting with a "/" were recognized.

Check this bug for more details (thanks to Sebo!)

  • Console - new :block command for blocking requests available in the Console panel (bug, thanks to thelehhman) Screenshot online
  • Infrastructure improvements
    • Getting rid of message manager & framescript (thanks to Neil Deakin, bug, bug, bug, bug)
    • Codebase cleanup - removing old RDM UI (frame script, browser element, viewport, etc.)
  • Fission - Making progress with a unified Resource layer. Good progress on DevTools client side and starting also with the backend (server side).
  • Individual DevTools panels/tools “watch” for specific resource types (console message, network request, debugger source, etc.) and get them from all debugged scopes automatically (content & main processes, workers, etc.)
  • Network Panel - Call for testing - support for Server Side Events (SSE) ready in 80. Visualization for text/event-stream content types (bug).

Behind a pref: devtools.netmonitor.features.sse

Use this test page #1

Use this test page #2 (with support for Mercure protocol)

Screenshot online


  • Fission newsletter 7 published
  • Down to only one legacy actor left (for print preview)
  • Visiting about:processes will now give information about running processes

Form Autofill

  • User Research on Credit Card Autofill completed

Installer & Updater

  • No updates today.


New Tab Page

  • A lot of previous things we’ve been testing for a while now and I’ve probably mentioned in the past are now on release or are about to be:
    • Pocket stories in newtab are now 100% on in the UK in release
    • V2 personalization is now 100% on in nightly and riding the trains. (previously was nightly only)
    • We’ve started to put in pocket sponsored content in Canada
    • Story collections are also available to be used in production, and we’ve used it once over the last little bit for the racial justice campaign we did.


  • `./mach node` (and `./mach npm`) now launches the node used by mach

Password Manager

(Menu in about:logins with the “Import from a File…” option)

(Login save doorhanger with a dropdown of username suggestions)

  • Kenrick fixed a few about:logins issues

PDFs & Printing


Performance Tools

  • No updates this week.


  • Planning has begun to do some experiments regarding improved discoverability of the Picture-in-Picture toggle
  • Gijs and mconley are putting together a proposal to mentor some MSU Capstone students on some Picture-in-Picture bugs in September


Remote Protocol (Chrome DevTools Protocol subset)

Search and Navigation


  • Search config modernization has been turned off in Firefox 78.0.1 due to a migration issue related to indexedDB (RemoteSettings) - Bug 1649558
  • Lots of modernization follow-up work, cleaning up the search service - Bug 1637744, Bug 1637931, Bug 1649426, Bug 1650756, Bug 1647320, Bug 1647359
  • The implementation of window.external.AddSearchProvider has been removed in Firefox 80, after this obsolete feature was disabled in Firefox 78 - Bug 1632448
  • Consumers of pref are being updated to use Region.jsm - Bug 1627540, Bug 1627547

Address Bar:

  • Hit a regression in Firefox 78 where profiles having a corrupt or locked places.sqlite couldn’t search or visit from the urlbar. A fallback path has been added from Firefox 78.0.2, restoring the previous behavior. We’re investigating follow-ups to help the users with those corruptions. - Bug 1649981
  • Various improvements to increase modularity of the querying code: Bug 1645521, Bug 1648468, Bug 1645324, Bug 1652040, Bug 1650099

User Journey

  • Launched about:welcome experiment in 78 with 2 screens (welcome and import)
    • Also testing new Amplitude integration and comparing with Redash
  • Adding additional experimental welcome screens for privacy and themes
  • Preparing some new default 80 welcome experience based on multistage findings
  • Turning on password import autocomplete suggestions by default in 80 with additional robustness over 77 experiment functionality (accessibility, localization)


This week I learned

  • [mconley] Avoid delete-ing properties on a JS Object. According to kmag, this puts the Object into “dictionary mode”, which has slower access characteristics. Best to set the value to null instead if possible.
    • For lazy getters, instead of using the “delete property, overwrite property” pattern, use something like defineLazyGetter.