Multi-level menu block styling in Bartik is not great

Adding a patch for the same with the attached before and after screenshots.

I checked this and didn't think the circles were necessary, nor adding a font size imho.
I also figured it would be a bit more scalable if we changed the padding to be in ems instead of px.
So basically the only thing this patch does is adding a padding of 1 em to the sub-menu's.

Before patch:

After patch:

This needs to work for RTL (right-to-left languages) as well. Also it would be great to see a screenshot of an expanded menu inside an expanded menu.

So, I checked everything by adding another expanded menu within the expanded menu.
I also set up a dummy RTL language set and to my great surprise the RTL works perfectly without any extra code.
In elements.css the nested ul and ol are already handled well on ln 143 to 151.
The code is in bartik/css/base/elements.css

ol ol,
ul ul {
  margin: 0;
  padding: 0 0 0.25em 1em; /* LTR */
}
[dir="rtl"] ol ol,
[dir="rtl"] ul ul {
  padding: 0 1em 0.25em 0;
}

I checked where it was going wrong in LTR and found that in two instances padding styles are added to only the LTR "ul.menu" element.
As far as I can tell, I can't seem to find a purpose yet as to why they are added.
They are:
in
bartik/css/components/menu.css (note that in rtl no padding styles are added)

/* This is needed to override ul.menu styles in menu.theme.css */
ul.menu {
  margin: 0;
  padding: 0 0 0.25em 0;
}

/* This is needed to override [dir="rtl"] ul.menu styles in menu.theme.css */
[dir="rtl"] ul.menu {
  margin: 0;
}
}

and in classy/css/components/menu.css (again note the lack of added padding styles for rtl)

ul.menu {
  list-style: none outside;
  margin-left: 1em; /* LTR */
  padding: 0;
  text-align: left; /* LTR */
}
[dir="rtl"] ul.menu {
  margin-left: 0;
  margin-right: 1em;
  text-align: right;
}

My proposal and Fix:

Remove the (apparently) redundant adding of 0 padding to the menu.css files in bartik and classy.
Find attached patch and screenshots.

RTL BEFORE & AFTER:

LTR BEFORE & AFTER PATCH:

Thanks @jhodgdon and @jordana; the screenshots are quite helpful.

+++ b/core/themes/stable/css/core/dropbutton/dropbutton.css
@@ -38,6 +38,10 @@
+/** when in quick edit mode **/
+#offcanvas td .dropbutton-widget {
+  position: inherit;
+}

#offcanvas is provided by an experimental module and AFAIK we should not put support for it in Stable. Maybe this fix is out of scope or belongs in Settings Tray (a.k.a. outside_in) CSS?

Ah, thanks @jhodgdon for clearing that up. So in the correct patch, there is just one change in Bartik and another in Classy.

The change in Bartik makes sense to me. However, Classy is supposed to be one of the stable base themes:

The stable base themes (Stable, Classy) are considered public API, with stable templates, markup, and CSS, so themes needing BC support should extend one of those base themes.

(From https://www.drupal.org/core/d8-bc-policy.)

Such a small whitespace change for a visual bugfix might be okay in a minor, but is it a required part of the fix?

Assigning to @Cottser for review.

For reference, the lines in Bartik were added with the whole file in #2548805: Add sensible base layout styles for lists in Bartik. and the line in Classy was similarly introduced with the whole file in #2395853: Split system.module.css and system.theme.css files into SMACSS style components.

Sorry for the delayed response, but this seems like a duplicate of #2607210: Visual regression: Sidebar menus are missing indentation styles., and we shouldn't be changing Classy, that's too risky. Since the other issue is much older, maybe we can inject some new energy into that one and close this as a duplicate. The other issue last I checked needed manual testing and screenshots. I can add issue credits for anyone who has worked on this issue to the other one if we agree it's a duplicate.

Thanks @xjm for the heads up on this.

@cottser I agree. I'll go ahead with whatever you guys think is the best way to tackle this. We can mark as duplicate and try to finally get this committed through the other issue :)