Correctly hook up back references to internalized strings in code deserializer.

test/mjsunit/deserialize-reference.js

Index: test/mjsunit/deserialize-reference.js
diff --git a/test/mjsunit/regress/regress-debug-context-load.js b/test/mjsunit/deserialize-reference.js
similarity index 67%
copy from test/mjsunit/regress/regress-debug-context-load.js
copy to test/mjsunit/deserialize-reference.js
index 0b3c275f99b016825cd563a700772bbddb7e4bad..b03201315932eab59e38c135d219192e6dcdf0eb 100644
--- a/test/mjsunit/regress/regress-debug-context-load.js
+++ b/test/mjsunit/deserialize-reference.js
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --expose-debug-as debug
+// Flags: --cache=code --serialize-toplevel
 
-Debug = debug.Debug;
-Debug.setListener(null);
+var a = "123";
+assertEquals(a, "123");