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diff --git a/security/sandbox/chromium/base/unguessable_token.h b/security/sandbox/chromium/base/unguessable_token.h
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+++ b/security/sandbox/chromium/base/unguessable_token.h
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+// Copyright 2016 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 BASE_UNGUESSABLE_TOKEN_H_
+#define BASE_UNGUESSABLE_TOKEN_H_
+
+#include <stdint.h>
+#include <string.h>
+#include <iosfwd>
+#include <tuple>
+
+#include "base/base_export.h"
+#include "base/hash/hash.h"
+#include "base/logging.h"
+#include "base/token.h"
+
+namespace base {
+
+struct UnguessableTokenHash;
+
+// UnguessableToken is, like Token, a randomly chosen 128-bit value. Unlike
+// Token, a new UnguessableToken is always generated at runtime from a
+// cryptographically strong random source (or copied or serialized and
+// deserialized from another such UnguessableToken). It can be used as part of a
+// larger aggregate type, or as an ID in and of itself.
+//
+// An UnguessableToken is a strong *bearer token*. Bearer tokens are like HTTP
+// cookies: if a caller has the token, the callee thereby considers the caller
+// authorized to request the operation the callee performs.
+//
+// UnguessableToken can be used when the resource associated with the ID needs
+// to be protected against manipulation by other untrusted agents in the system,
+// and there is no other convenient way to verify the authority of the agent to
+// do so (because the resource is part of a table shared across processes, for
+// instance). In such a scheme, knowledge of the token value in and of itself is
+// sufficient proof of authority to carry out an operation on the associated
+// resource.
+//
+// Use Create() for creating new UnguessableTokens.
+//
+// NOTE: It is illegal to send empty UnguessableTokens across processes, and
+// sending/receiving empty tokens should be treated as a security issue. If
+// there is a valid scenario for sending "no token" across processes, use
+// base::Optional instead of an empty token.
+
+class BASE_EXPORT UnguessableToken {
+ public:
+  // Create a unique UnguessableToken.
+  static UnguessableToken Create();
+
+  // Returns a reference to a global null UnguessableToken. This should only be
+  // used for functions that need to return a reference to an UnguessableToken,
+  // and should not be used as a general-purpose substitute for invoking the
+  // default constructor.
+  static const UnguessableToken& Null();
+
+  // Return a UnguessableToken built from the high/low bytes provided.
+  // It should only be used in deserialization scenarios.
+  //
+  // NOTE: If the deserialized token is empty, it means that it was never
+  // initialized via Create(). This is a security issue, and should be handled.
+  static UnguessableToken Deserialize(uint64_t high, uint64_t low);
+
+  // Creates an empty UnguessableToken.
+  // Assign to it with Create() before using it.
+  constexpr UnguessableToken() = default;
+
+  // NOTE: Serializing an empty UnguessableToken is an illegal operation.
+  uint64_t GetHighForSerialization() const {
+    DCHECK(!is_empty());
+    return token_.high();
+  }
+
+  // NOTE: Serializing an empty UnguessableToken is an illegal operation.
+  uint64_t GetLowForSerialization() const {
+    DCHECK(!is_empty());
+    return token_.low();
+  }
+
+  bool is_empty() const { return token_.is_zero(); }
+
+  // Hex representation of the unguessable token.
+  std::string ToString() const { return token_.ToString(); }
+
+  explicit operator bool() const { return !is_empty(); }
+
+  bool operator<(const UnguessableToken& other) const {
+    return token_ < other.token_;
+  }
+
+  bool operator==(const UnguessableToken& other) const {
+    return token_ == other.token_;
+  }
+
+  bool operator!=(const UnguessableToken& other) const {
+    return !(*this == other);
+  }
+
+ private:
+  friend struct UnguessableTokenHash;
+  explicit UnguessableToken(const Token& token);
+
+  base::Token token_;
+};
+
+BASE_EXPORT std::ostream& operator<<(std::ostream& out,
+                                     const UnguessableToken& token);
+
+// For use in std::unordered_map.
+struct UnguessableTokenHash {
+  size_t operator()(const base::UnguessableToken& token) const {
+    DCHECK(token);
+    return TokenHash()(token.token_);
+  }
+};
+
+}  // namespace base
+
+#endif  // BASE_UNGUESSABLE_TOKEN_H_