Add an identity component for unique/opaque url::Origins.

url/origin.h

 // Copyright 2015 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 URL_ORIGIN_H_
 #define URL_ORIGIN_H_
 
 #include <stdint.h>
 
 #include <string>
 
 #include "base/strings/string16.h"
 #include "base/strings/string_piece.h"
+#include "base/unguessable_token.h"
 #include "url/scheme_host_port.h"
 #include "url/third_party/mozilla/url_parse.h"
 #include "url/url_canon.h"
 #include "url/url_constants.h"
 #include "url/url_export.h"
 
 class GURL;
 
 namespace url {
 
@@ skipping 143 matching lines @@
          base::StringPiece host,
          uint16_t port,
          base::StringPiece suborigin,
          SchemeHostPort::ConstructPolicy policy);
   Origin(std::string scheme,
          std::string host,
          uint16_t port,
          std::string suborigin,
          SchemeHostPort::ConstructPolicy policy);
 
+  bool unique_;
+
   SchemeHostPort tuple_;
-  bool unique_;
   std::string suborigin_;
+
+  // This should only be used for equality comparison when both origins are
+  // unique.
+  base::UnguessableToken unique_id_;
 };
 
 URL_EXPORT std::ostream& operator<<(std::ostream& out, const Origin& origin);
 
 URL_EXPORT bool IsSameOriginWith(const GURL& a, const GURL& b);
 URL_EXPORT bool IsSamePhysicalOriginWith(const GURL& a, const GURL& b);
 
 }  // namespace url
 
 #endif  // URL_ORIGIN_H_