Inherit EventTarget interface instead of duplicating its code

Source/modules/encryptedmedia/MediaKeySession.idl

Index: Source/modules/encryptedmedia/MediaKeySession.idl
diff --git a/Source/modules/encryptedmedia/MediaKeySession.idl b/Source/modules/encryptedmedia/MediaKeySession.idl
index 57b809ec018a7ca19a9b29b64139f2a7df99a0cd..3afc689f8881d3d526838bec43fcdaae266da7e1 100644
--- a/Source/modules/encryptedmedia/MediaKeySession.idl
+++ b/Source/modules/encryptedmedia/MediaKeySession.idl
@@ -25,9 +25,8 @@
 
 [
     Conditional=ENCRYPTED_MEDIA_V2,
-    EnabledAtRuntime=encryptedMedia,
-    EventTarget
-] interface MediaKeySession {
+    EnabledAtRuntime=encryptedMedia
+] interface MediaKeySession : EventTarget {
     // error state
     readonly attribute MediaKeyError error;
 
@@ -43,13 +42,4 @@
     [EnabledAtRuntime=encryptedMedia] attribute EventListener onwebkitkeyadded;
     [EnabledAtRuntime=encryptedMedia] attribute EventListener onwebkitkeyerror;
     [EnabledAtRuntime=encryptedMedia] attribute EventListener onwebkitkeymessage;
-
-    // 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);
 };