Add helper function to test that a given URL is a valid Gaia sign in URL.

google_apis/gaia/gaia_auth_util.h

 // Copyright (c) 2012 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.
 
 #ifndef GOOGLE_APIS_GAIA_GAIA_AUTH_UTIL_H_
 #define GOOGLE_APIS_GAIA_GAIA_AUTH_UTIL_H_
 
 #include <string>
 
+class GURL;
+
 namespace gaia {
 
 // Perform basic canonicalization of |email_address|, taking into account that
 // gmail does not consider '.' or caps inside a username to matter. It also
 // ignores everything after a '+'. For example, c.masone+abc@gmail.com ==
 // cMaSone@gmail.com, per
 // http://mail.google.com/support/bin/answer.py?hl=en&ctx=mail&answer=10313#
 std::string CanonicalizeEmail(const std::string& email_address);
 
 // Returns the canonical form of the given domain.
 std::string CanonicalizeDomain(const std::string& domain);
 
 // Sanitize emails. Currently, it only ensures all emails have a domain by
 // adding gmail.com if no domain is present.
 std::string SanitizeEmail(const std::string& email_address);
 
 // Extract the domain part from the canonical form of the given email.
 std::string ExtractDomainName(const std::string& email);
 
+bool IsGaiaSignonRealm(const GURL& url);
+
 }  // namespace gaia
 
 #endif  // GOOGLE_APIS_GAIA_GAIA_AUTH_UTIL_H_