Remove implicit conversions from scoped_refptr to T* in sandbox/

sandbox/linux/bpf_dsl/cons_unittest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "sandbox/linux/bpf_dsl/cons.h"
 
 #include <string>
 
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace sandbox {
 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;
 }
 
 TEST(ConsListTest, Basic) {
   Cons<char>::List ba =
       Cons<char>::Make('b', Cons<char>::Make('a', Cons<char>::List()));
   EXPECT_EQ("ba", Join(ba));
 
   Cons<char>::List cba = Cons<char>::Make('c', ba);
   Cons<char>::List dba = Cons<char>::Make('d', ba);
   EXPECT_EQ("cba", Join(cba));
   EXPECT_EQ("dba", Join(dba));
 }
 
 }  // namespace
 }  // namespace sandbox