Always treat .localhost as loopback

net/dns/host_resolver_proc.cc

Index: net/dns/host_resolver_proc.cc
diff --git a/net/dns/host_resolver_proc.cc b/net/dns/host_resolver_proc.cc
index f2b10c649bad49e5d083024a45e04594f91324f6..15b4b56ce06648ae88fd129fb117cec2193f60cf 100644
--- a/net/dns/host_resolver_proc.cc
+++ b/net/dns/host_resolver_proc.cc
@@ -11,6 +11,7 @@
 #include "net/base/address_list.h"
 #include "net/base/dns_reloader.h"
 #include "net/base/net_errors.h"
+#include "net/base/net_util.h"
 #include "net/base/sys_addrinfo.h"
 
 #if defined(OS_OPENBSD)
@@ -189,7 +190,11 @@ int SystemHostResolverCall(const std::string& host,
     !defined(OS_ANDROID)
   DnsReloaderMaybeReload();
 #endif
-  int err = getaddrinfo(host.c_str(), NULL, &hints, &ai);
+
+  // Redirect .localhost queries to localhost to make sure that they are
+  // never sent out on the network, per RFC 6761.
+  int err = getaddrinfo(IsLocalhostTLD(host) ? "localhost" : host.c_str(), NULL,
+                        &hints, &ai);
   bool should_retry = false;
   // If the lookup was restricted (either by address family, or address
   // detection), and the results where all localhost of a single family,