diff -r 000000000000 -r 6474c204b198 xpcom/glue/nsClassHashtable.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/xpcom/glue/nsClassHashtable.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,117 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsClassHashtable_h__
+#define nsClassHashtable_h__
+
+#include "nsBaseHashtable.h"
+#include "nsHashKeys.h"
+#include "nsAutoPtr.h"
+
+/**
+ * templated hashtable class maps keys to C++ object pointers.
+ * See nsBaseHashtable for complete declaration.
+ * @param KeyClass a wrapper-class for the hashtable key, see nsHashKeys.h
+ *   for a complete specification.
+ * @param Class the class-type being wrapped
+ * @see nsInterfaceHashtable, nsClassHashtable
+ */
+template<class KeyClass,class T>
+class nsClassHashtable :
+  public nsBaseHashtable< KeyClass, nsAutoPtr<T>, T* >
+{
+public:
+  typedef typename KeyClass::KeyType KeyType;
+  typedef T* UserDataType;
+  typedef nsBaseHashtable< KeyClass, nsAutoPtr<T>, T* > base_type;
+
+  nsClassHashtable()
+  {
+  }
+  explicit nsClassHashtable(uint32_t aInitSize)
+    : nsBaseHashtable<KeyClass,nsAutoPtr<T>,T*>(aInitSize)
+  {
+  }
+
+  /**
+   * @copydoc nsBaseHashtable::Get
+   * @param pData if the key doesn't exist, pData will be set to nullptr.
+   */
+  bool Get(KeyType aKey, UserDataType* pData) const;
+
+  /**
+   * @copydoc nsBaseHashtable::Get
+   * @returns nullptr if the key is not present.
+   */
+  UserDataType Get(KeyType aKey) const;
+
+  /**
+   * Remove the entry for the given key from the hashtable and return it in
+   * aOut.  If the key is not in the hashtable, aOut's pointer is set to
+   * nullptr.
+   *
+   * Normally, an entry is deleted when it's removed from an nsClassHashtable,
+   * but this function transfers ownership of the entry back to the caller
+   * through aOut -- the entry will be deleted when aOut goes out of scope.
+   *
+   * @param aKey the key to get and remove from the hashtable
+   */
+  void RemoveAndForget(KeyType aKey, nsAutoPtr<T> &aOut);
+};
+
+//
+// nsClassHashtable definitions
+//
+
+template<class KeyClass,class T>
+bool
+nsClassHashtable<KeyClass,T>::Get(KeyType aKey, T** retVal) const
+{
+  typename base_type::EntryType* ent = this->GetEntry(aKey);
+
+  if (ent)
+  {
+    if (retVal)
+      *retVal = ent->mData;
+
+    return true;
+  }
+
+  if (retVal)
+    *retVal = nullptr;
+
+  return false;
+}
+
+template<class KeyClass,class T>
+T*
+nsClassHashtable<KeyClass,T>::Get(KeyType aKey) const
+{
+  typename base_type::EntryType* ent = this->GetEntry(aKey);
+
+  if (!ent)
+    return nullptr;
+
+  return ent->mData;
+}
+
+template<class KeyClass,class T>
+void
+nsClassHashtable<KeyClass,T>::RemoveAndForget(KeyType aKey, nsAutoPtr<T> &aOut)
+{
+  aOut = nullptr;
+  nsAutoPtr<T> ptr;
+
+  typename base_type::EntryType *ent = this->GetEntry(aKey);
+  if (!ent)
+    return;
+
+  // Transfer ownership from ent->mData into aOut.
+  aOut = ent->mData;
+
+  this->Remove(aKey);
+}
+
+#endif // nsClassHashtable_h__