We currently do this only for known built-in buttons. It makes sense to assume that we'll want the same if we add another menu button, and to treat add-on buttons the same way. Johann, want to take this? It will make bug 1352358 easier.

Sure.

Comment on attachment 8870024 [details] Bug 1366550 - Hide the dropdown arrow of type=menu and type=panel buttons in the navbar. https://reviewboard.mozilla.org/r/141546/#review145132 ::: browser/themes/shared/toolbarbuttons.inc.css:116 (Diff revision 1) > -moz-appearance: none; > padding: 0; > margin: 0; > } > > -#nav-bar .toolbarbutton-1:not([type=menu-button]), > +#nav-bar .toolbarbutton-1, Need to keep :not([type=menu-button]) here. type=menu-button is different from type=menu. ::: browser/themes/shared/toolbarbuttons.inc.css:194 (Diff revision 1) > #nav-bar .toolbarbutton-1 > .toolbarbutton-menubutton-button > .toolbarbutton-icon { > border-inline-end-style: none; > } > > -#nav-bar .toolbarbutton-1[type=panel] > .toolbarbutton-icon, > -#nav-bar .toolbarbutton-1[type=panel] > .toolbarbutton-badge-stack, > +#nav-bar .toolbarbutton-1[type=menu] > .toolbarbutton-menu-dropmarker, > +#nav-bar .toolbarbutton-1[type=panel] > .toolbarbutton-menu-dropmarker { #nav-bar .toolbarbutton-1 > .toolbarbutton-menu-dropmarker

Pushed by jhofmann@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/b0e00320b59a Hide the dropdown arrow of type=menu and type=panel buttons in the navbar. r=dao

Out of curiosity, was there a reason to do this only on the nav-bar? What happens if users customize buttons to the tabstrip or bookmarks toolbar?

(In reply to :Gijs from comment #7) > Out of curiosity, was there a reason to do this only on the nav-bar? What > happens if users customize buttons to the tabstrip or bookmarks toolbar? We only do it where we apply the toolbarbutton-1 styling (otherwise we fall back to native). If/when we make that include the bookmarks toolbar, we should hide the dropmarker there too. The tabs toolbar is included as of <https://hg.mozilla.org/mozilla-central/rev/be624d4f3f132c032429381517a2e736563dac38>.