Have bindings layer assume and insist that all interface types are GCed.

third_party/WebKit/Source/modules/indexeddb/IDBIndex.idl

 /*
  * Copyright (C) 2010 Google 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
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  * 2.  Redistributions in binary form must reproduce the above copyright
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  *
  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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 // https://w3c.github.io/IndexedDB/#idl-def-IDBIndex
 
 [
     Exposed=(Window,Worker),
-    GarbageCollected
 ] interface IDBIndex {
     readonly attribute DOMString name;
     readonly attribute IDBObjectStore objectStore;
     [CallWith=ScriptState] readonly attribute any keyPath;
     readonly attribute boolean multiEntry;
     readonly attribute boolean unique;
 
     [CallWith=ScriptState, RaisesException] IDBRequest get(any key);
     [CallWith=ScriptState, RaisesException] IDBRequest getKey(any key);
     // TODO(cmumford): 0xFFFFFFFF is not necessary. Remove once crbug.com/335871 is fixed.
     [CallWith=ScriptState, RaisesException] IDBRequest getAll([Default=Undefined] optional any range, optional unsigned long maxCount = 0xFFFFFFFF);
     // TODO(cmumford): 0xFFFFFFFF is not necessary. Remove once crbug.com/335871 is fixed.
     [CallWith=ScriptState, RaisesException] IDBRequest getAllKeys([Default=Undefined] optional any range, [EnforceRange] optional unsigned long maxCount = 0xFFFFFFFF);
     [CallWith=ScriptState, RaisesException] IDBRequest count([Default=Undefined] optional any key);
     [CallWith=ScriptState, RaisesException] IDBRequest openCursor([Default=Undefined] optional any range, optional IDBCursorDirection direction = "next");
     [CallWith=ScriptState, RaisesException] IDBRequest openKeyCursor([Default=Undefined] optional any range, optional IDBCursorDirection direction = "next");
 
 };