diff -r 000000000000 -r 6474c204b198 mfbt/tests/TestWeakPtr.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mfbt/tests/TestWeakPtr.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,79 @@
+/* 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/. */
+
+#include "mozilla/WeakPtr.h"
+
+using mozilla::SupportsWeakPtr;
+using mozilla::WeakPtr;
+
+// To have a class C support weak pointers, inherit from SupportsWeakPtr<C>.
+class C : public SupportsWeakPtr<C>
+{
+  public:
+    MOZ_DECLARE_REFCOUNTED_TYPENAME(C)
+    int num;
+    void act() {}
+};
+
+static void
+Example()
+{
+
+  C* ptr =  new C();
+
+  // Get weak pointers to ptr. The first time asWeakPtr is called
+  // a reference counted WeakReference object is created that
+  // can live beyond the lifetime of 'ptr'. The WeakReference
+  // object will be notified of 'ptr's destruction.
+  WeakPtr<C> weak = ptr->asWeakPtr();
+  WeakPtr<C> other = ptr->asWeakPtr();
+
+  // Test a weak pointer for validity before using it.
+  if (weak) {
+    weak->num = 17;
+    weak->act();
+  }
+
+  // Destroying the underlying object clears weak pointers to it.
+  delete ptr;
+
+  MOZ_RELEASE_ASSERT(!weak, "Deleting |ptr| clears weak pointers to it.");
+  MOZ_RELEASE_ASSERT(!other, "Deleting |ptr| clears all weak pointers to it.");
+}
+
+struct A : public SupportsWeakPtr<A>
+{
+    MOZ_DECLARE_REFCOUNTED_TYPENAME(A)
+    int data;
+};
+
+
+int
+main()
+{
+
+  A* a = new A;
+
+  // a2 is unused to test the case when we haven't initialized
+  // the internal WeakReference pointer.
+  A* a2 = new A;
+
+  a->data = 5;
+  WeakPtr<A> ptr = a->asWeakPtr();
+  {
+      WeakPtr<A> ptr2 = a->asWeakPtr();
+      MOZ_RELEASE_ASSERT(ptr->data == 5);
+      WeakPtr<A> ptr3 = a->asWeakPtr();
+      MOZ_RELEASE_ASSERT(ptr->data == 5);
+  }
+
+  delete a;
+  MOZ_RELEASE_ASSERT(!ptr);
+
+  delete a2;
+
+  Example();
+
+  return 0;
+}