Auto merge of #22676 - ferjm:textrack.activecues, r=jdm

Expose TextTrack.activeCues

- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #22675

This only exposes the `activeCues` property to make sure that `/html/semantics/embedded-content/media-elements/track/track-element/track-active-cues.html` timeouts consistently.

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components/script/dom/texttrack.rs

@@ -110,6 +110,13 @@ impl TextTrackMethods for TextTrack {
         }
     }
 
+    // https://html.spec.whatwg.org/multipage/#dom-texttrack-activecues
+    fn GetActiveCues(&self) -> Option<DomRoot<TextTrackCueList>> {
+        // XXX implement active cues logic
+        //      https://github.com/servo/servo/issues/22314
+        None
+    }
+
     // https://html.spec.whatwg.org/multipage/#dom-texttrack-addcue
     fn AddCue(&self, cue: &TextTrackCue) -> ErrorResult {
         // FIXME(#22314, dlrobertson) add Step 1 & 2

components/script/dom/webidls/TextTrack.webidl

@@ -19,7 +19,7 @@ interface TextTrack : EventTarget {
   attribute TextTrackMode mode;
 
   readonly attribute TextTrackCueList? cues;
-  // readonly attribute TextTrackCueList? activeCues;
+  readonly attribute TextTrackCueList? activeCues;
 
   [Throws]
   void addCue(TextTrackCue cue);