system-api: Add cryptohome NeedsDircryptoMigration name

BUG=chromium:706307
TEST=None.

Change-Id: I75f45bab9de5b56d4a0991c3f8c48fcc5ee9f6fc
Reviewed-on: https://chromium-review.googlesource.com/473528
Commit-Ready: Xiyuan Xia <xiyuan@chromium.org>
Tested-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Kazuhiro Inaba <kinaba@chromium.org>
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
diff --git a/dbus/cryptohome/dbus-constants.h b/dbus/cryptohome/dbus-constants.h
index 0c20c63..4300eb5 100644
--- a/dbus/cryptohome/dbus-constants.h
+++ b/dbus/cryptohome/dbus-constants.h
@@ -123,6 +123,7 @@
 const char kCryptohomeRemoveFirmwareManagementParameters[] =
     "RemoveFirmwareManagementParameters";
 const char kCryptohomeMigrateToDircrypto[] = "MigrateToDircrypto";
+const char kCryptohomeNeedsDircryptoMigration[] = "NeedsDircryptoMigration";
 
 // Signals
 const char kSignalAsyncCallStatus[] = "AsyncCallStatus";