diff -r 000000000000 -r 4f2f89ce4247 WebCore/bindings/js/JSDebugWrapperSet.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/WebCore/bindings/js/JSDebugWrapperSet.h	Fri Sep 17 09:02:29 2010 +0300
@@ -0,0 +1,88 @@
+/*
+ * 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
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. 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 DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef JSDebugWrapperSet_h
+#define JSDebugWrapperSet_h
+
+#include "JSDOMWrapper.h"
+#include <wtf/HashSet.h>
+#include <wtf/Noncopyable.h>
+
+namespace WebCore {
+
+// For debugging, keep a set of wrappers currently cached, and check that
+// all are uncached before they are destroyed. This helps us catch bugs like:
+//     - wrappers being deleted without being removed from the cache
+//     - wrappers being cached twice
+
+class JSDebugWrapperSet : public Noncopyable {
+    friend class WTF::ThreadSpecific<JSDebugWrapperSet>;
+public:
+    static JSDebugWrapperSet& shared();
+
+    void add(DOMObject* object) { m_wrapperSet.add(object); }
+    void remove(DOMObject* object) { m_wrapperSet.remove(object); }
+    bool contains(DOMObject* object) const { return m_wrapperSet.contains(object); }
+
+    static void willCacheWrapper(DOMObject*);
+    static void didUncacheWrapper(DOMObject*);
+
+private:
+    JSDebugWrapperSet();
+
+    HashSet<DOMObject*> m_wrapperSet;
+};
+
+#ifdef NDEBUG
+
+inline void JSDebugWrapperSet::willCacheWrapper(DOMObject*)
+{
+}
+
+inline void JSDebugWrapperSet::didUncacheWrapper(DOMObject*)
+{
+}
+
+#else
+
+inline void JSDebugWrapperSet::willCacheWrapper(DOMObject* wrapper)
+{
+    ASSERT(!JSDebugWrapperSet::shared().contains(wrapper));
+    JSDebugWrapperSet::shared().add(wrapper);
+}
+
+inline void JSDebugWrapperSet::didUncacheWrapper(DOMObject* wrapper)
+{
+    if (!wrapper)
+        return;
+    ASSERT(JSDebugWrapperSet::shared().contains(wrapper));
+    JSDebugWrapperSet::shared().remove(wrapper);
+}
+
+#endif
+
+} // namespace WebCore
+
+#endif // JSDebugWrapperSet_h