Use MarkIndependent in sample shell.

samples/shell.cc

Index: samples/shell.cc
diff --git a/samples/shell.cc b/samples/shell.cc
index 3640fa013982b96fb2dae1b1d6a6b09cff7e735c..342031db885bd88439303f118aece568a4995f8d 100644
--- a/samples/shell.cc
+++ b/samples/shell.cc
@@ -504,6 +504,7 @@ v8::Handle<v8::Value> CreateExternalArray(const v8::Arguments& args,
   v8::Persistent<v8::Object> persistent_array =
       v8::Persistent<v8::Object>::New(array);
   persistent_array.MakeWeak(data, ExternalArrayWeakCallback);
+  persistent_array.MarkIndependent();
   array->SetIndexedPropertiesToExternalArrayData(data, type, length);
   array->Set(v8::String::New("length"), v8::Int32::New(length),
              v8::ReadOnly);