Make the DOMStringMap deleter return type void

Source/core/dom/DOMStringMap.idl

 /*
  * Copyright (C) 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 14 matching lines @@
 
 // https://html.spec.whatwg.org/#the-domstringmap-interface
 
 [
     OverrideBuiltins,
     SetWrapperReferenceFrom=element,
     WillBeGarbageCollected,
 ] interface DOMStringMap {
     [ImplementedAs=item] getter DOMString (DOMString name);
     [RaisesException] setter void (DOMString name, DOMString value);
-    // FIXME: The deleter return type should be void. crbug.com/462920
-    deleter boolean (DOMString name);
+    deleter void (DOMString name);
 
     // FIXME: The indexed getter, setter and deleter are not in the
     // spec and simply converts the index to a string.
     [NotEnumerable] getter DOMString (unsigned long index);
     [RaisesException] setter void (unsigned long index, DOMString value);
-    deleter boolean (unsigned long index);
+    deleter void (unsigned long index);
 };