Fix "passing NULL to non-pointer argument" warning in gcc 4.1

net/base/host_resolver_unittest.cc

 // Copyright (c) 2006-2008 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 "net/base/host_resolver.h"
 #include "net/base/address_list.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 #ifdef OS_WIN
 #include <ws2tcpip.h>
@@ skipping 11 matching lines @@
 TEST(HostResolverTest, NumericAddresses) {
   // Stevens says dotted quads with AI_UNSPEC resolve to a single sockaddr_in.
 
   net::HostResolver host_resolver;
   net::AddressList adrlist;
   const int kPortnum = 5555;
   int err = host_resolver.Resolve("127.0.0.1", kPortnum, &adrlist, NULL);
   EXPECT_EQ(0, err);
 
   const struct addrinfo* ainfo = adrlist.head();
-  EXPECT_EQ(NULL, ainfo->ai_next);
+  EXPECT_EQ(static_cast<addrinfo*>(NULL), ainfo->ai_next);
   EXPECT_EQ(sizeof(struct sockaddr_in), ainfo->ai_addrlen);
 
   const struct sockaddr* sa = ainfo->ai_addr;
   const struct sockaddr_in* sa_in = (const struct sockaddr_in*) sa;
   EXPECT_EQ(htons(kPortnum), sa_in->sin_port);
   EXPECT_EQ(htonl(0x7f000001), sa_in->sin_addr.s_addr);
 }
 
 } // namespace