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

net/base/ip_address.h

 // Copyright (c) 2015 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_ADDRESS_NET_H_
 #define NET_BASE_IP_ADDRESS_NET_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 51 matching lines @@
   // Returns true if |ip_address_| is an IPv4-mapped IPv6 address.
   bool IsIPv4MappedIPv6() const;
 
   // The size in bytes of |ip_address_|.
   size_t size() const { return ip_address_.size(); }
 
   // Returns true if the IP is an empty, zero-sized (invalid) address.
   bool empty() const { return ip_address_.empty(); }
 
   // Returns the canonical string representation of an IP address.
-  // For example: "192.168.0.1" or "::1". The IP address must be
-  // valid, calling this on an invalid address will result in a crash.
+  // For example: "192.168.0.1" or "::1". Returns the empty string when
+  // |ip_address_| is invalid.
   std::string ToString() const;
 
   // Parses an IP address literal (either IPv4 or IPv6) to its numeric value.
   // Returns true on success and fills |ip_address_| with the numeric value.
   bool AssignFromIPLiteral(const base::StringPiece& ip_literal)
       WARN_UNUSED_RESULT;
 
   // Returns the underlying byte vector.
   const std::vector<uint8_t>& bytes() const { return ip_address_; };
 
@@ skipping 39 matching lines @@
 // In cases when an IPv4 address is being compared to an IPv6 address prefix
 // and vice versa, the IPv4 addresses will be converted to IPv4-mapped
 // (IPv6) addresses.
 NET_EXPORT bool IPAddressMatchesPrefix(const IPAddress& ip_address,
                                        const IPAddress& ip_prefix,
                                        size_t prefix_length_in_bits);
 
 }  // namespace net
 
 #endif  // NET_BASE_IP_ADDRESS_NET_H_