IPEndPoint::ToString should not crash when the IP address is empty.

net/base/ip_endpoint.h

 // 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.
 
 #ifndef NET_BASE_IP_ENDPOINT_H_
 #define NET_BASE_IP_ENDPOINT_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 35 matching lines @@
   bool ToSockAddr(struct sockaddr* address, socklen_t* address_length) const
       WARN_UNUSED_RESULT;
 
   // Convert from a sockaddr struct.
   // |address| is the address.
   // |address_length| is the length of |address|.
   // Returns true on success, false on failure.
   bool FromSockAddr(const struct sockaddr* address, socklen_t address_length)
       WARN_UNUSED_RESULT;
 
-  // Returns value as a string (e.g. "127.0.0.1:80"). Returns empty
-  // string if the address is invalid, and cannot not be converted to a
-  // string.
+  // Returns value as a string (e.g. "127.0.0.1:80"). The IP address must be
+  // valid.
   std::string ToString() const;
 
   // As above, but without port.
   std::string ToStringWithoutPort() const;
 
   bool operator<(const IPEndPoint& that) const;
   bool operator==(const IPEndPoint& that) const;
 
  private:
   IPAddressNumber address_;
   uint16 port_;
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_IP_ENDPOINT_H_