Lazily register prototype users

test/cctest/test-heap.cc

Index: test/cctest/test-heap.cc
diff --git a/test/cctest/test-heap.cc b/test/cctest/test-heap.cc
index 8858a82d9adf7f838a0add8538918278d1ba7748..9cada2f0e57fc22c03062a8e703eb9c645f41359 100644
--- a/test/cctest/test-heap.cc
+++ b/test/cctest/test-heap.cc
@@ -5369,3 +5369,15 @@ TEST(Regress472513) {
   TestRightTrimFixedTypedArray(i::kExternalUint16Array, 8 - 1, 3);
   TestRightTrimFixedTypedArray(i::kExternalUint32Array, 4, 3);
 }
+
+
+TEST(WeakFixedArray) {
+  CcTest::InitializeVM();
+  v8::HandleScope scope(CcTest::isolate());
+
+  Handle<HeapNumber> number = CcTest::i_isolate()->factory()->NewHeapNumber(1);
+  Handle<WeakFixedArray> array = WeakFixedArray::Add(Handle<Object>(), number);
+  array->Remove(number);
+  array->Compact();
+  WeakFixedArray::Add(array, number);
+}