Inherit EventTarget interface instead of duplicating its code

Source/modules/mediastream/MediaStreamTrack.idl

Index: Source/modules/mediastream/MediaStreamTrack.idl
diff --git a/Source/modules/mediastream/MediaStreamTrack.idl b/Source/modules/mediastream/MediaStreamTrack.idl
index d02d8ed833e5da36548ef6d71e4520c55cb58641..c2df9f92c57def491f688ac74a64760b20ae282b 100644
--- a/Source/modules/mediastream/MediaStreamTrack.idl
+++ b/Source/modules/mediastream/MediaStreamTrack.idl
@@ -23,9 +23,8 @@
  */
 
 [
-    EventTarget,
     ActiveDOMObject
-] interface MediaStreamTrack {
+] interface MediaStreamTrack : EventTarget {
     readonly attribute DOMString kind;
     readonly attribute DOMString id;
     readonly attribute DOMString label;
@@ -38,14 +37,5 @@
     attribute EventListener onended;
 
     [CallWith=ScriptExecutionContext, RaisesException] static void getSources(MediaStreamTrackSourcesCallback callback);
-
-    // EventTarget interface
-    void addEventListener(DOMString type,
-                          EventListener listener,
-                          optional boolean useCapture);
-    void removeEventListener(DOMString type,
-                             EventListener listener,
-                             optional boolean useCapture);
-    [RaisesException] boolean dispatchEvent(Event event);
 };