Auto merge of #12495 - ice9js:implement-runnable-for-PauseIfNotInDocumentTask, r=KiChjang

Implement Runnable trait name method for PauseIfNotInDocumentTask

Implements #12350.

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components/script/dom/htmlmediaelement.rs

@@ -801,6 +801,8 @@ impl PauseIfNotInDocumentTask {
 }
 
 impl Runnable for PauseIfNotInDocumentTask {
+    fn name(&self) -> &'static str { "PauseIfNotInDocumentTask" }
+
     fn handler(self: Box<PauseIfNotInDocumentTask>) {
         let elem = self.elem.root();
         if !elem.upcast::<Node>().is_in_doc() {