[net/dns] Resolve AF_UNSPEC on dual-stacked systems. Sort addresses according to RFC3484.

net/dns/dns_client.h

Index: net/dns/dns_client.h
diff --git a/net/dns/dns_client.h b/net/dns/dns_client.h
index c5461ec3fdc0911440285f887a238fa62e441dd4..d79cb126f566c7f0c78fb3c1ef29b19c7aef7981 100644
--- a/net/dns/dns_client.h
+++ b/net/dns/dns_client.h
@@ -11,6 +11,7 @@
 
 namespace net {
 
+class AddressSorter;
 struct DnsConfig;
 class DnsTransactionFactory;
 class NetLog;
@@ -30,6 +31,8 @@ class NET_EXPORT DnsClient {
   // Returns NULL if the current config is not valid.
   virtual DnsTransactionFactory* GetTransactionFactory() = 0;
 
+  virtual AddressSorter* GetAddressSorter() = 0;
+
   // Creates default client.
   static scoped_ptr<DnsClient> CreateClient(NetLog* net_log);
 };