[Linux] Enable connecting to localhost when offline.

net/base/host_resolver_proc.cc

Index: net/base/host_resolver_proc.cc
diff --git a/net/base/host_resolver_proc.cc b/net/base/host_resolver_proc.cc
index 804135cbf1f8d08935850486bb1c51aa3a8e1b2d..8e8034f455a0d64bca0dbe42b24c3b2b9186ef6b 100644
--- a/net/base/host_resolver_proc.cc
+++ b/net/base/host_resolver_proc.cc
@@ -216,6 +216,12 @@ int SystemHostResolverProc(const std::string& host,
   hints.ai_flags = AI_ADDRCONFIG;
 #endif
 
+  // On Linux AI_ADDRCONFIG doesn't consider loopback addreses, even if only
+  // loopback addresses are configured. So don't use it when there are only
+  // loopback addresses.
+  if (host_resolver_flags & HOST_RESOLVER_LOOPBACK_ONLY)
+    hints.ai_flags &= ~AI_ADDRCONFIG;
+
   if (host_resolver_flags & HOST_RESOLVER_CANONNAME)
     hints.ai_flags |= AI_CANONNAME;