Remove "Default Address Family" behavior from the HostResolver.

net/dns/host_resolver_impl.h

Index: net/dns/host_resolver_impl.h
diff --git a/net/dns/host_resolver_impl.h b/net/dns/host_resolver_impl.h
index e6a7a6db73f23f34874e41bddd78db126880a040..e3b8ed7685ea5b935287a4a405e9769b45938ddf 100644
--- a/net/dns/host_resolver_impl.h
+++ b/net/dns/host_resolver_impl.h
@@ -135,8 +135,6 @@ class NET_EXPORT HostResolverImpl
                        AddressList* addresses,
                        const BoundNetLog& source_net_log) override;
   void CancelRequest(RequestHandle req) override;
-  void SetDefaultAddressFamily(AddressFamily address_family) override;
-  AddressFamily GetDefaultAddressFamily() const override;
   void SetDnsClientEnabled(bool enabled) override;
   HostCache* GetHostCache() override;
   base::Value* GetDnsConfigAsValue() const override;
@@ -205,7 +203,7 @@ class NET_EXPORT HostResolverImpl
   // Probes IPv6 support and returns true if IPv6 support is enabled.
   // Results are cached, i.e. when called repeatedly this method returns result
   // from the first probe for some time before probing again.
-  bool IsIPv6Reachable(const BoundNetLog& net_log);
+  virtual bool IsIPv6Reachable(const BoundNetLog& net_log);
 
   // Records the result in cache if cache is present.
   void CacheResult(const Key& key,
@@ -268,9 +266,6 @@ class NET_EXPORT HostResolverImpl
 
   NetLog* net_log_;
 
-  // Address family to use when the request doesn't specify one.
-  AddressFamily default_address_family_;
-
   // If present, used by DnsTask and ServeFromHosts to resolve requests.
   scoped_ptr<DnsClient> dns_client_;
 
@@ -281,10 +276,6 @@ class NET_EXPORT HostResolverImpl
   // Number of consecutive failures of DnsTask, counted when fallback succeeds.
   unsigned num_dns_failures_;
 
-  // True if probing is done for each Request to set address family. When false,
-  // explicit setting in |default_address_family_| is used.
-  bool probe_ipv6_support_;
-
   // True if DnsConfigService detected that system configuration depends on
   // local IPv6 connectivity. Disables probing.
   bool use_local_ipv6_;