List.sortBy produces different order between Chromium/Chrome and Firefox

index.elm

module Main exposing (..)

import Html exposing (div, text)
import List
import Tuple


main =
    Html.beginnerProgram { model = [], view = view, update = (\_ -> \x -> x) }


view _ =
    div [] <| List.map (div [] << List.singleton << text << Tuple.first) (List.sortBy Tuple.second tuples)


tuples =
    [ ( "1", "foo" )
    , ( "2", "bar" )
    , ( "3", "foo" )
    , ( "4", "foo" )
    , ( "5", "foo" )
    , ( "6", "baz" )
    , ( "7", "foo" )
    , ( "8", "quux" )
    , ( "9", "foo" )
    , ( "10", "foo" )
    , ( "11", "foo" )
    ]

Chromium/Chrome 66.0.3359.139:

2
6
3
4
5
1
7
10
9
11
8

Firefox 59.0.2:

2
6
1
3
4
5
7
9
10
11
8

Tested on Linux.