[Linux] Enable connecting to localhost when offline.

net/base/net_util.h

Index: net/base/net_util.h
diff --git a/net/base/net_util.h b/net/base/net_util.h
index 5633c11ef5b0973abbc3f6a0eb967bedfd688463..978d4fbc0b1f5219dec77365ef308d418f5aa309 100644
--- a/net/base/net_util.h
+++ b/net/base/net_util.h
@@ -327,6 +327,10 @@ void SetExplicitlyAllowedPorts(const std::wstring& allowed_ports);
 // TODO(jar): Make test more in-depth as needed.
 bool IPv6Supported();
 
+// Returns true if it can determine that only loopback addresses are configured.
+// i.e. if only 127.0.0.1 and ::1 are routable.
+bool HaveOnlyLoopbackAddresses();
+
 // IPAddressNumber is used to represent an IP address's numeric value as an
 // array of bytes, from most significant to least significant. This is the
 // network byte ordering.