Inherit EventTarget interface instead of duplicating its code

Source/core/html/track/TextTrackCue.idl

Index: Source/core/html/track/TextTrackCue.idl
diff --git a/Source/core/html/track/TextTrackCue.idl b/Source/core/html/track/TextTrackCue.idl
index 962f695a8ea0b269a78c1e15dccacd55e5af1ccb..f398a9a99a1c9ca0b771a9fbdd02f6cd73b586df 100644
--- a/Source/core/html/track/TextTrackCue.idl
+++ b/Source/core/html/track/TextTrackCue.idl
@@ -26,9 +26,8 @@
 [
     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;
@@ -49,15 +48,6 @@
     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;
 };