Specifically these preferences:

dom.storage.next_gen

dom.max_script_run_time
dom.max_chrome_script_run_time

converter.html2txt.always_include_ruby

plugin.mousewheel.enabled
mousewheel.autodir.enabled
mousewheel.autodir.honourroot
accessibility.accesskeycausesactivation
ui.click_hold_context_menus

dom.experimental_forms
dom.forms.datetime.others
dom.forms.color

dom.noopener.newprocess.enabled

dom.testing.ignore_ipc_principal

DOM: Core isn't quite right, but it feels closer to the right component than General, given that these prefs are all under dom/.

Depends on D77846

NOTE: this also removes a mysterious old comment that implied this code could run without libpref initializing
the value, in which case they picked a different default. I assume this is no longer a real configuration?

Depends on D77847

converts:

• plugin.mousewheel.enabled
• mousewheel.autodir.enabled
• mousewheel.autodir.honourroot
• accessibility.accesskeycausesactivation
• ui.click_hold_context_menus

Depends on D77848

converts:

• dom.experimental_forms
• dom.forms.datetime.others
• dom.forms.color

Depends on D77849

Depends on D77850

Depends on D77851

clean try build: https://treeherder.mozilla.org/pushhealth.html?revision=2b3f018cf614a2e92030db1cdae088cc2c04b6a6&repo=try

patches now ready to review

This review comment raises an interesting question about the next_storage pref, and how pref initialization works, that I need to investigate further. I suggest we land the other patches in the interim, to avoid bitrot.

https://hg.mozilla.org/mozilla-central/rev/d804de3225b0
https://hg.mozilla.org/mozilla-central/rev/c02b43c5cf49
https://hg.mozilla.org/mozilla-central/rev/5b40ba91c89a
https://hg.mozilla.org/mozilla-central/rev/cd600940f441
https://hg.mozilla.org/mozilla-central/rev/191e6bda6d77
https://hg.mozilla.org/mozilla-central/rev/6943a06706ca