[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 13aa0bf8ed1183320180b4482110a15540df6e93..650c7d0d4166aee2f0591a4fb0edd6663474bdd0 100644
--- a/net/dns/dns_client.h
+++ b/net/dns/dns_client.h
@@ -10,12 +10,14 @@
 
 namespace net {
 
+class AddressSorter;
 struct DnsConfig;
 class DnsTransactionFactory;
 class NetLog;
 
-// Convenience wrapper allows easy injection of DnsTransaction into
-// HostResolverImpl.
+// Convenience wrapper which allows easy injection of DnsTransaction into
+// HostResolverImpl. Pointers returned by the Get* methods are only guaranteed
+// to remain valid until next time SetConfig is called.
 class NET_EXPORT DnsClient {
  public:
   virtual ~DnsClient() {}
@@ -29,6 +31,9 @@ class NET_EXPORT DnsClient {
   // Returns NULL if the current config is not valid.
   virtual DnsTransactionFactory* GetTransactionFactory() = 0;
 
+  // Returns NULL if the current config is not valid.
+  virtual AddressSorter* GetAddressSorter() = 0;
+
   // Creates default client.
   static scoped_ptr<DnsClient> CreateClient(NetLog* net_log);
 };