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

MozReview-Commit-ID: 4dIykkUdIxZ

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);
                 }
             })

tests/wpt/mozilla/meta/MANIFEST.json

@@ -27152,7 +27152,7 @@
    "testharness"
   ],
   "mozilla/getComputedStyle.html": [
-   "17a1592664bdc9518786673683b9c43412fe9424",
+   "0cb74e3ff46837ccc308fac608f6924f101a0da6",
    "testharness"
   ],
   "mozilla/getPropertyPriority.html": [

tests/wpt/mozilla/tests/mozilla/getComputedStyle.html

@@ -6,6 +6,7 @@
         <style>
             #foo:before {
                 color: red;
+                content: "";
             }
 
             #foo {