Auto merge of #17426 - aethanyc:fix-has-author-specified-rules-xbl, r…

…=heycam

stylo: Fix has_author_specified_rules() for rules in XBL stylesheets

This change is reviewed in https://bugzilla.mozilla.org/show_bug.cgi?id=1372062

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components/style/rule_tree/mod.rs

@@ -1112,8 +1112,7 @@ impl StrongRuleNode {
                     CascadeLevel::UANormal |
                     CascadeLevel::UAImportant |
                     CascadeLevel::UserNormal |
-                    CascadeLevel::UserImportant |
-                    CascadeLevel::XBL => {
+                    CascadeLevel::UserImportant  => {
                         for (id, declaration) in longhands {
                             if properties.contains(id) {
                                 // This property was set by a non-author rule.
@@ -1136,6 +1135,7 @@ impl StrongRuleNode {
                     }
                     // Author rules:
                     CascadeLevel::PresHints |
+                    CascadeLevel::XBL |
                     CascadeLevel::AuthorNormal |
                     CascadeLevel::StyleAttributeNormal |
                     CascadeLevel::SMILOverride |