Implement contextmenu attribute with basic support of <menu>

Source/core/events/RelatedEvent.idl

Index: Source/core/events/RelatedEvent.idl
diff --git a/Source/core/events/RelatedEvent.idl b/Source/core/events/RelatedEvent.idl
new file mode 100644
index 0000000000000000000000000000000000000000..3065aaab0b998dcab1b9cedeca8d957d528a58f0
--- /dev/null
+++ b/Source/core/events/RelatedEvent.idl
@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2006, 2007 Apple Inc. All rights reserved.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public License
+ * along with this library; see the file COPYING.LIB.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */

[esprehn, 2014/05/20 05:51:34]

short copyright

[pals, 2014/05/21 07:55:12]

Done.

+
+[
+    EventConstructor,
+] interface RelatedEvent : Event {
+    [InitializedByEventConstructor] readonly attribute EventTarget ? relatedTarget;

[esprehn, 2014/05/20 05:51:34]

no space before ?

[pals, 2014/05/21 07:55:12]

Done.

+};
+