Inherit EventTarget interface instead of duplicating its code

Source/core/page/EventSource.idl

Index: Source/core/page/EventSource.idl
diff --git a/Source/core/page/EventSource.idl b/Source/core/page/EventSource.idl
index 490161e9265445903f1fd48a5f98cf241e7b5fcb..d92caa9df7030dadae98a93f3f97c648eed1bdfa 100644
--- a/Source/core/page/EventSource.idl
+++ b/Source/core/page/EventSource.idl
@@ -34,9 +34,8 @@
     ActiveDOMObject,
     Constructor(DOMString url, optional Dictionary eventSourceInit),
     ConstructorCallWith=ScriptExecutionContext,
-    ConstructorRaisesException,
-    EventTarget
-] interface EventSource {
+    ConstructorRaisesException
+] interface EventSource : EventTarget {
 
     readonly attribute DOMString URL; // Lowercased .url is the one in the spec, but leaving .URL for compatibility reasons.
     readonly attribute DOMString url;
@@ -53,14 +52,4 @@
     attribute EventListener onmessage;
     attribute EventListener onerror;
     void close();
-
-    // 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);
-
 };