Sun Valley breaks style of autoscroll indicator (when middle click on page)

[emvaized]

Here's how it looks:

How it's supposed to look:

I belive these lines from base.css are to blame — when you comment them out, autoscroll style is fixed, but all navbar popups become broken (such as "Add to bookmarks" popup, Downloads popup, etc):

@media (-moz-windows-compositor) {
    .panel-arrowbox + slot[part="content"] {
        margin: 0px !important;
        box-shadow: none !important;
        background-clip: padding-box !important;
        border: 1px solid var(--uwp-context-border) !important;
    }

    slot[part="content"]:only-child {
        margin: var(--uwp-popup-padding) !important;
        border: 1px solid var(--uwp-context-border) !important;
        border-radius: var(--uwp-tags-overlay-radius) !important;
        background: var(--uwp-context-background) !important;
        background-clip: padding-box !important;
        box-shadow: var(--uwp-shadow-context) !important;
        overflow: clip !important;
    }
}

[emvaized]

It turns out, replacing background: with background-color: solves the issue with non-visible icon:

But still, the stylying is broken due to clipped content and squary shape

[Guerra24]

Hi, this is a known issue that is unfixable right now, sorry.

Duplicate of #56