Add an opt-out header for HTTP throttling. Never throttle for localhost.

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 935eab672778500cc95ba5bb733ca41e73f4edfc..5bf5998ef95d1a40497307be3fe974c2f2727202 100644
--- a/net/base/net_util.h
+++ b/net/base/net_util.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
@@ -423,6 +423,14 @@ const uint16* GetPortFieldFromSockaddr(const struct sockaddr* address,
 int GetPortFromSockaddr(const struct sockaddr* address,
                         socklen_t address_len);
 
+// Returns true if |host| is "localhost" or one of the IP-address
+// representations of the loopback address (IPv4 127.0.0.0/8 or IPv6 ::1).
+//
+// Note that this function does not check for IP addresses other than
+// the above being mapped back to the local machine, it only checks
+// for those exact IP addresses.
+bool IsLocalhost(const std::string& host);
+
 }  // namespace net
 
 #endif  // NET_BASE_NET_UTIL_H_