Keep the module in scope when executing scripts. This prevents a crash when the

webkit/plugins/ppapi/ppapi_plugin_instance.cc

Index: webkit/plugins/ppapi/ppapi_plugin_instance.cc
===================================================================
--- webkit/plugins/ppapi/ppapi_plugin_instance.cc	(revision 81764)
+++ webkit/plugins/ppapi/ppapi_plugin_instance.cc	(working copy)
@@ -664,6 +664,8 @@
   NPVariant result;
   bool ok = WebBindings::evaluate(NULL, frame->windowObject(), &np_script,
                                   &result);
+  // DANGER! |this| could be deleted at this point if the script removed the
+  // plugin from the DOM.
   if (!ok) {
     // TODO(brettw) bug 54011: The TryCatch isn't working properly and
     // doesn't actually catch this exception.