Auto merge of #15495 - prampey:mql-borrow-error, r=jdm

Calling matchMedia during a MQL change event will not panic

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Calling matchMedia now leads to a new copy of MQL objects to prevent errors when borrowing references from MQL during an MQL change event.

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #14967  (github issue number if applicable).

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- [X] There are tests for these changes OR
- [x] These changes do not require tests because _____

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components/script/dom/mediaquerylist.rs

@@ -138,17 +138,23 @@ impl WeakMediaQueryListVec {
     /// Evaluate media query lists and report changes
     /// https://drafts.csswg.org/cssom-view/#evaluate-media-queries-and-report-changes
     pub fn evaluate_and_report_changes(&self) {
+        rooted_vec!(let mut mql_list);
         self.cell.borrow_mut().update(|mql| {
             let mql = mql.root().unwrap();
             if let MediaQueryListMatchState::Changed(_) = mql.evaluate_changes() {
-                let event = MediaQueryListEvent::new(&mql.global(),
-                                                     atom!("change"),
-                                                     false, false,
-                                                     mql.Media(),
-                                                     mql.Matches());
-                event.upcast::<Event>().fire(mql.upcast::<EventTarget>());
+                // Recording list of changed Media Queries
+                mql_list.push(JS::from_ref(&*mql));
             }
         });
+        // Sending change events for all changed Media Queries
+        for mql in mql_list.iter() {
+            let event = MediaQueryListEvent::new(&mql.global(),
+                                                 atom!("change"),
+                                                 false, false,
+                                                 mql.Media(),
+                                                 mql.Matches());
+            event.upcast::<Event>().fire(mql.upcast::<EventTarget>());
+        }
     }
 }