Inherit EventTarget interface instead of duplicating its code

Source/core/html/track/TextTrackCue.idl

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 [
     EnabledAtRuntime=videoTrack,
     Constructor(double startTime, double endTime, DOMString text),
-    ConstructorCallWith=ScriptExecutionContext,
-    EventTarget
-] interface TextTrackCue {
+    ConstructorCallWith=ScriptExecutionContext
+] interface TextTrackCue : EventTarget {
     readonly attribute TextTrack track;
 
     attribute DOMString id;
     [SetterRaisesException] attribute double startTime;
     [SetterRaisesException] attribute double endTime;
     attribute boolean pauseOnExit;
 
     [SetterRaisesException] attribute DOMString vertical;
     attribute boolean snapToLines;
     [SetterRaisesException] attribute long line;
     [SetterRaisesException] attribute long position;
     [SetterRaisesException] attribute long size;
     [SetterRaisesException] attribute DOMString align;
 
     attribute DOMString text;
     DocumentFragment getCueAsHTML();
 
     attribute EventListener onenter;
     attribute EventListener onexit;
 
-    // EventTarget interface
-    void addEventListener(DOMString type,
-                          EventListener listener,
-                          optional boolean useCapture);
-    void removeEventListener(DOMString type,
-                             EventListener listener,
-                             optional boolean useCapture);
-    [RaisesException] boolean dispatchEvent(Event evt);
-
     [Conditional=WEBVTT_REGIONS] attribute DOMString regionId;
 };