Auto merge of #13453 - metajack:media-query-list, r=jdm

Implement matchMedia and MediaQueryList

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #13376 (github issue number if applicable).

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Fixes #13376.

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components/script/dom/webidls/MediaQueryList.webidl

@@ -0,0 +1,14 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// https://drafts.csswg.org/cssom-view/#mediaquerylist
+
+[Exposed=(Window)]
+interface MediaQueryList : EventTarget {
+  readonly attribute DOMString media;
+  readonly attribute boolean matches;
+  void addListener(EventListener? listener);
+  void removeListener(EventListener? listener);
+           attribute EventHandler onchange;
+};

components/script/dom/webidls/Window.webidl

@@ -120,7 +120,7 @@ dictionary ScrollToOptions : ScrollOptions {
 
 // http://dev.w3.org/csswg/cssom-view/#extensions-to-the-window-interface
 partial interface Window {
-  //MediaQueryList matchMedia(DOMString query);
+  [Exposed=(Window), NewObject] MediaQueryList matchMedia(DOMString query);
   [SameObject] readonly attribute Screen screen;
 
   // browsing context