Sync the EventSource interface with the spec

Source/core/page/EventSourceInit.idl

Index: Source/core/page/EventSourceInit.idl
diff --git a/Source/core/page/EventSourceInit.idl b/Source/core/page/EventSourceInit.idl
index 8e713e505d33f9c7cefea3974733ab6e50c6b542..f4594e8f47a549f0dcb0b4c8499e95b2ae1d7a03 100644
--- a/Source/core/page/EventSourceInit.idl
+++ b/Source/core/page/EventSourceInit.idl
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// https://html.spec.whatwg.org/multipage/comms.html#the-eventsource-interface
+
 dictionary EventSourceInit {
     boolean withCredentials = false;
 };