Remove implicit conversions from scoped_refptr to T* in sandbox/

sandbox/linux/bpf_dsl/cons_unittest.cc

Index: sandbox/linux/bpf_dsl/cons_unittest.cc
diff --git a/sandbox/linux/bpf_dsl/cons_unittest.cc b/sandbox/linux/bpf_dsl/cons_unittest.cc
index 790cae081208a33914c79e970c03760987b5e79e..571e767b91090b3d1287643496516903abc8dc43 100644
--- a/sandbox/linux/bpf_dsl/cons_unittest.cc
+++ b/sandbox/linux/bpf_dsl/cons_unittest.cc
@@ -13,7 +13,7 @@ namespace {
 
 std::string Join(Cons<char>::List char_list) {
   std::string res;
-  for (Cons<char>::List it = char_list; it; it = it->tail()) {
+  for (Cons<char>::List it = char_list; it.get(); it = it->tail()) {
     res.push_back(it->head());
   }
   return res;