Always treat .localhost as loopback

net/base/net_util.cc

Index: net/base/net_util.cc
diff --git a/net/base/net_util.cc b/net/base/net_util.cc
index 3b49dffb5c20d889003a09755276ddaa8e41542d..40c33b8c2d37695ce7bf4bbbb3c17a8f3f813ec2 100644
--- a/net/base/net_util.cc
+++ b/net/base/net_util.cc
@@ -144,6 +144,9 @@ static const int kAllowedFtpPorts[] = {
   22,   // ssh
 };
 
+static const char kLocalhostTLD[] = ".localhost.";
+static const size_t kLocalhostTLDLength = strlen(kLocalhostTLD);
+
 bool IPNumberPrefixCheck(const IPAddressNumber& ip_number,
                          const unsigned char* ip_prefix,
                          size_t prefix_length_in_bits) {
@@ -984,7 +987,8 @@ bool IsLocalhost(const std::string& host) {
   if (host == "localhost" ||
       host == "localhost.localdomain" ||
       host == "localhost6" ||
-      host == "localhost6.localdomain6")
+      host == "localhost6.localdomain6" ||
+      IsLocalhostTLD(host))
     return true;
 
   IPAddressNumber ip_number;
@@ -1014,6 +1018,24 @@ bool IsLocalhost(const std::string& host) {
   return false;
 }
 
+bool IsLocalhostTLD(const std::string& host) {
+  size_t host_length = host.length();
+
+  // First try to match against ".localhost", then against ".localhost."
+  // with the trailing dot.
+
+  if (host_length < kLocalhostTLDLength - 1)
+    return false;
+  if (host.compare(host_length - kLocalhostTLDLength + 1, std::string::npos,
+                   kLocalhostTLD, 0, kLocalhostTLDLength - 1) == 0)
+    return true;
+
+  if (host_length < kLocalhostTLDLength)
+    return false;
+  return host.compare(host_length - kLocalhostTLDLength, std::string::npos,
+                      kLocalhostTLD) == 0;
+}
+
 NetworkInterface::NetworkInterface()
     : type(NetworkChangeNotifier::CONNECTION_UNKNOWN), prefix_length(0) {
 }