Buggy behavior with Psuedeo CSS class and new servo engine

Firefox Nightly
#1

When

layout.css.servo.enabled = true

I get this:

16 PM
Screen Shot 2017-09-28 at 11.11.16 PM.png592×1044 22 KB

When:

layout.css.servo.enabled = false

I get this:

58 PM
Screen Shot 2017-09-28 at 11.10.58 PM.png598×1080 30.7 KB

The CSS not being applied under the servo engine is:

.wp-color-result::after {
    background: #f7f7f7;
    -webkit-border-radius: 0 2px 2px 0;
    border-radius: 0 2px 2px 0;
    border-left: 1px solid #ccc;
    color: #555;
    content: attr( title );
    display: block;
    font-size: 11px;
    line-height: 22px;
    padding: 0 6px;
    position: relative;
    right: 0;
    text-align: center;
    top: 0;
}

However, it does work on other WordPress sites under different domains when servo is enabled. I suspect there might be a strange caching issue within the servo engine and my development environment.

Any thoughts?

#2

To replicate the issue:
For that page go on WordPress->Appearance-> Customizer but you need to have a theme that use that.

As WP Developer maybe there is other stuff that conflict if happen only on a specific site. Maybe a plugin that add stuff?

#3

You can use the default Twentyseventeen WordPress theme, which has a color option.

I don’t think it is a plugin issue, since the problem goes away when I turn servo off. The problem occurred immediately after my Firefox update.