ChromeOS: Add RenameCryptohome and migration code.

chromeos/dbus/fake_cryptohome_client.h

Index: chromeos/dbus/fake_cryptohome_client.h
diff --git a/chromeos/dbus/fake_cryptohome_client.h b/chromeos/dbus/fake_cryptohome_client.h
index 20402dcde42eea3385c02f033d6e65dc537c2fb9..9fb1f493e9a693440d328df663bc71c85dc02997 100644
--- a/chromeos/dbus/fake_cryptohome_client.h
+++ b/chromeos/dbus/fake_cryptohome_client.h
@@ -38,6 +38,9 @@ class CHROMEOS_EXPORT FakeCryptohomeClient : public CryptohomeClient {
                        const AsyncMethodCallback& callback) override;
   void AsyncRemove(const cryptohome::Identification& cryptohome_id,
                    const AsyncMethodCallback& callback) override;
+  void RenameCryptohome(const cryptohome::Identification& cryptohome_id_from,
+                        const cryptohome::Identification& cryptohome_id_to,
+                        const ProtobufMethodCallback& callback) override;
   void GetSystemSalt(const GetSystemSaltCallback& callback) override;
   void GetSanitizedUsername(const cryptohome::Identification& cryptohome_id,
                             const StringDBusMethodCallback& callback) override;