Fix for bug 604362 (Don't rewrap XPCWrappedNatives that don't have classinfo). r=mrbkap.

js/src/xpconnect/tests/unit/test_bug604362.js

@@ -0,0 +1,12 @@
+function run_test() {
+  var Cc = Components.classes;
+  var Ci = Components.interfaces;
+  var sp = Cc["@mozilla.org/systemprincipal;1"].
+           createInstance(Ci.nsIPrincipal);
+  var s = Components.utils.Sandbox(sp);
+  s.a = [];
+  s.Cu = Components.utils;
+  s.C = Components;
+  s.do_check_neq = do_check_neq;
+  Components.utils.evalInSandbox("do_check_neq(Cu.import, undefined);", s);
+}

js/src/xpconnect/wrappers/WrapperFactory.cpp

@@ -108,6 +108,11 @@ WrapperFactory::PrepareForWrapping(JSContext *cx, JSObject *scope, JSObject *obj
 
     XPCWrappedNative *wn = static_cast<XPCWrappedNative *>(xpc_GetJSPrivate(obj));
 
+    // If the object doesn't have classinfo we want to return the same
+    // XPCWrappedNative so that we keep the same set of interfaces.
+    if (!wn->GetClassInfo())
+        return DoubleWrap(cx, obj, flags);
+
     // We know that DOM objects only allow one object, we can return early.
     if (wn->HasProto() && wn->GetProto()->ClassIsDOMObject())
         return DoubleWrap(cx, obj, flags);