Make IP Address related functions return the empty string when used on an invalid address.

net/base/ip_endpoint_unittest.cc

 // Copyright (c) 2012 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/ip_endpoint.h"
 
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
 #include <winsock2.h>
@@ skipping 180 matching lines @@
   IPEndPoint endpoint;
   EXPECT_EQ(0, endpoint.port());
 
   for (uint16_t index = 0; index < test_count; ++index) {
     uint16_t port = 100 + index;
     IPEndPoint endpoint(tests[index].ip_address, port);
     const std::string result = endpoint.ToString();
     EXPECT_EQ(tests[index].host_normalized + ":" + base::UintToString(port),
               result);
   }
+
+  // ToString() shouldn't crash on invalid addresses.
+  IPAddress invalid_address;
+  IPEndPoint invalid_endpoint(invalid_address, 8080);
+  EXPECT_EQ("", invalid_endpoint.ToString());
+  EXPECT_EQ("", invalid_endpoint.ToStringWithoutPort());
 }
 
 }  // namespace
 
 }  // namespace net