Inherit EventTarget interface instead of duplicating its code

Source/core/html/track/TextTrackList.idl

Index: Source/core/html/track/TextTrackList.idl
diff --git a/Source/core/html/track/TextTrackList.idl b/Source/core/html/track/TextTrackList.idl
index 905efc3293c5689ba52a1e8cc838c18dd815ca5e..a6e51b3e62ca752736560c504d8afd88f4346b96 100644
--- a/Source/core/html/track/TextTrackList.idl
+++ b/Source/core/html/track/TextTrackList.idl
@@ -25,20 +25,11 @@
 
 [
     EnabledAtRuntime=videoTrack,
-    EventTarget,
     GenerateIsReachable=owner
-] interface TextTrackList {
+] interface TextTrackList : EventTarget {
     readonly attribute unsigned long length;
     getter TextTrack item(unsigned long index);
 
     attribute EventListener onaddtrack;
-
-    void addEventListener(DOMString type,
-                          EventListener listener,
-                          optional boolean useCapture);
-    void removeEventListener(DOMString type,
-                             EventListener listener,
-                             optional boolean useCapture);
-    [RaisesException] boolean dispatchEvent(Event evt);
 };