Auto merge of #18261 - emilio:silly-pseudo-style, r=heycam

style: Really only resolve applicable ::before / ::after.

<!-- Reviewable:start -->
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/18261)
<!-- Reviewable:end -->

components/style/style_resolver.rs

@@ -194,7 +194,12 @@ where
                     &primary_style,
                     layout_parent_style_for_pseudo
                 );
+
                 if let Some(style) = pseudo_style {
+                    if !matches!(self.pseudo_resolution, PseudoElementResolution::Force) &&
+                       eager_pseudo_is_definitely_not_generated(&pseudo, &style) {
+                        return;
+                    }
                     pseudo_styles.set(&pseudo, style);
                 }
             })