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Draft: Bug 282: Move `--disable-eme` to OS- and architecture-specific mozconfigs

Merge Info

Related Issues



  • Immediate: patchset needed as soon as possible
  • Next Minor Stable Release: patchset that needs to be verified in nightly before backport
  • Eventually: patchset that needs to be verified in alpha before backport
  • No Backport (preferred): patchset for the next major stable

(Optional) Justification

  • Emergency security update: patchset fixes CVEs, 0-days, etc
  • Critical bug-fix: patchset fixes a bug in core-functionality
  • Consistency: patchset which would make development easier if it were in both the alpha and release branches; developer tools, build system changes, etc
  • Sponsor required: patchset required for sponsor
  • Localization: typos and other localization changes that should be also in the release branch
  • Other: please explain


  • Merge to mullvad-browser - !fixups to mullvad-browser-specific commits, new features, security backports
  • Merge to base-browser -!fixups to base-browser-specific commits, new features to be shared with tor-browser
    • NOTE: if your changeset includes patches to both base-browser and mullvad-browser please clearly label in the change description which commits should be cherry-picked to base-browser after merging

Issue Tracking


Request Reviewer

  • Request review from an applications developer depending on modified system:
    • NOTE: if the MR modifies multiple areas, please /cc all the relevant reviewers (since gitlab only allows 1 reviewer)
    • accessibility : henry
    • android : clairehurst, dan
    • build system : boklm
    • extensions : ma1
    • firefox internals (XUL/JS/XPCOM) : ma1
    • fonts : pierov
    • frontend (implementation) : henry
    • frontend (review) : donuts, richard
    • localization : henry, pierov
    • macos : clairehurst, dan
    • nightly builds : boklm
    • rebases/release-prep : dan, ma1, pierov, richard
    • security : ma1
    • signing : boklm, richard
    • updater : pierov
    • misc/other : pierov, richard

Change Description

Note: this is a twin MR of tor-browser!971 (merged).

This MR moves the --disable-eme Firefox configuration option from the base-browser mozconfig to the mozconfigs of targets which support it. At the moment, these are all the desktop targets for which the Mullvad Browser is built. linux-arm (which is not built) and linux-aarch64 (which is a work in progress) do not support --disable-eme, so their mozconfigs must not contain this option. As discussed in issue #282 (closed), when not supported, no --disable-eme option is equivalent to --disable-eme itself (i.e. EMEs are already disabled).

How Tested

grep -RI "browser/config/mozconfigs/base-browser" # discover who uses the base-browser mozconfig
grep -RI "browser/config/mozconfigs/mullvad-browser" # discover who uses the mullvad-browser mozconfig

Then added --disable-eme to every mozconfig that imports base-browser (except for mozconfig-linux-arm, which in any case is not built) and removed it from base-browser itself. I tested this is equivalent to the current configuration by building the Mullvad Browser for linux-x86_64 (./mach build using mozconfig-linux-x86-64-dev) and looking for the relevant entries in about:config.

Edited by Pier Angelo Vendrame

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