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Today’s meeting leader is: johannh

General Topics / Roundtable

  • [standard8] Firefox source docs site has had the top-level rearranged slightly. Now all browser/ docs are under the Firefox section.
  • [mconley] We have a new Fission-compatible replacement for ContentTask.spawn - SpecialPowers.spawn. The main differences being that it can target OOP subframes, can run in test content scripts, and that the arguments must be passed as an Array. Documentation here, and some tests demonstrating its usage.

Friends of the Firefox team


  • [mconley] Emma Malysz was an intern last summer who worked on XBL removal, and has returned to join us full time! She started last week in SF.

Resolved bugs (excluding employees)

Fixed more than one bug

  • Arun Kumar Mohan
  • Dennis van der Schagt [:dennisschagt]
  • Dhyey Thakore [:dhyey35]
  • Florens Verschelde :fvsch
  • Heng Yeow (:tanhengyeow)
  • Itiel
  • Krishnal Ciccolella
  • Megha [ :meghaaa ]
  • Priyank Singh

New contributors (🌟 = first patch)

Project Updates

Add-ons / Web Extensions


Warnings on conflicting extension shortcuts (screenshot link)


Inspecting storage.local data on an installed extension (screenshot link)


  • Firefox Accounts

    • No updates.

  • Sync and Storage

    • No updates.

  • Push

    • No updates.

Browser Architecture

  • No updates.

Developer Tools

(Screenshots will be replaced by links after the meeting)


  • DOM Mutation Breakpoints - this features allows the user to pause JS execution when DOM structure changes (Subtree/attribute modification or node removal). It’s now available behind a flag and ready for testing. You need to flip the two following prefs to enable it:

    • devtools.debugger.features.dom-mutation-breakpoints devtools.markup.mutationBreakpoints.enabled


Screenshot link


Screenshot link

  • Inline Previews - showing actual variable values inline. This feature is also available behind a flag and ready for testing. You need to flip the following pref to enable it:

    • Devtools.debugger.features.inline-preview


Note the inline boxes showing actual variable values

Screenshot link

  • Disable debugger; statement - It is now possible to disable a debugger statement via a false-conditional breakpoint created at the same location (bug).


  • WebSocket Inspection (GSoC project) - This feature is enabled on Nightly by default (devtools.netmonitor.features.webSockets)

    • Supported protocols Socket.IO, SockJS, plain JSON (and MQTT soon)

    • WS frames Filtering supported (by type & by free text)

    • A test page


Screenshot link

  • Heads Up: Search across all files/cookies/headers in the Network panel coming soon! (Outreachy)

Perf Tools

  • JavaScript Allocations - tracking for JS allocations added. It's still experimental but you can enable it by checking "JS Allocations" in recording panel feature flags


Screenshot link

Accessibility Panel

  • A new option to auto-scroll to the selected node in the panel tree [Yura]
  • The UI was re-organized a bit [Yura]


Screenshot link



  • ESLint has been updated to 6.1.0 (from 5.16.0). This helped us with a few things:

    • Running --fix over the entire tree should now work for pretty much everything that's auto-fixable. Previously it would stop working at the `js/` directories, and then you'd have to run it manually on the remaining sub-directories (e.g. services, toolkit etc etc).

    • If you have an /* global foo */ statement for ESLint and foo is unused, it will now throw an error.

    • There's also now a new rule enabled on most of the tree: no-async-promise-executor. This aims to avoid issues with having asynchronous functions within new Promise()

  • ESLint will also be upgraded to 6.2.2 within the next couple of days. The main addition here is support for BigInt and dynamic imports.

New Tab Page

  • 69 we’re launching “Discovery Stream” which is a newtab experience with more pocket content. We’re doing this with a rollout on Sept 10th.
  • Trying to ensure 70 is good to go, we want to run some revenue experiments in 70 for promo content, which requires some new features.

Password Manager


Performance Tools

  • No update this week


Policy Engine (read only)

  • No updates


Search and Navigation

User Journey

This week I learned

  • [johannh] I forgot: pbz added a new module for testing permissions (PermissionTestUtils), that you should use

    • [MattN] Permission manager test* APIs don’t currently check OriginAttributes