Add SecureMessage definitions to CryptAuth.

components/proximity_auth/cryptauth/fake_secure_message_delegate.h

Index: components/proximity_auth/cryptauth/fake_secure_message_delegate.h
diff --git a/components/proximity_auth/cryptauth/fake_secure_message_delegate.h b/components/proximity_auth/cryptauth/fake_secure_message_delegate.h
new file mode 100644
index 0000000000000000000000000000000000000000..ad8b21b48cd2c59b5d373bd2014b469951ad8329
--- /dev/null
+++ b/components/proximity_auth/cryptauth/fake_secure_message_delegate.h
@@ -0,0 +1,51 @@
+// 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 COMPONENTS_PROXIMITY_AUTH_FAKE_SECURE_MESSAGE_DELEGATE_H
+#define COMPONENTS_PROXIMITY_AUTH_FAKE_SECURE_MESSAGE_DELEGATE_H
+
+#include "base/macros.h"
+#include "components/proximity_auth/cryptauth/secure_message_delegate.h"
+
+namespace proximity_auth {
+
+// Fake implementation of SecureMessageDelegate used in tests.
+// For clarity in tests, all functions in this delegate will invoke their
+// callback with the result before returning.
+class FakeSecureMessageDelegate : public SecureMessageDelegate {
+ public:
+  FakeSecureMessageDelegate();
+  ~FakeSecureMessageDelegate() override;
+
+  // SecureMessageDelegate:
+  void GenerateKeyPair(const GenerateKeyPairCallback& callback) override;
+  void DeriveKey(const std::string& private_key,
+                 const std::string& public_key,
+                 const DeriveKeyCallback& callback) override;
+  void CreateSecureMessage(
+      const std::string& payload,
+      const std::string& key,
+      const CreateOptions& create_options,
+      const CreateSecureMessageCallback& callback) override;
+  void UnwrapSecureMessage(
+      const std::string& serialized_message,
+      const std::string& key,
+      const UnwrapOptions& unwrap_options,
+      const UnwrapSecureMessageCallback& callback) override;
+
+  // Sets the next public key to be returned by GenerateKeyPair(). The
+  // corresponding private key will be derived from this public key.
+  void set_next_public_key(const std::string& public_key) {
+    next_public_key_ = public_key;
+  }
+
+ private:
+  std::string next_public_key_;
+
+  DISALLOW_COPY_AND_ASSIGN(FakeSecureMessageDelegate);
+};
+
+}  // namespace proximity_auth
+
+#endif  // COMPONENTS_PROXIMITY_AUTH_FAKE_SECURE_MESSAGE_DELEGATE_H