Move definition of PasswordType enum to a separate header.

components/sync/base/passphrase_type.cc

Index: components/sync/base/passphrase_type.cc
diff --git a/components/sync/base/passphrase_type.cc b/components/sync/base/passphrase_type.cc
new file mode 100644
index 0000000000000000000000000000000000000000..cdebb90b2b213f6dfcb4339866c502188e773613
--- /dev/null
+++ b/components/sync/base/passphrase_type.cc
@@ -0,0 +1,14 @@
+// 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.
+
+#include "components/sync/base/passphrase_type.h"
+
+namespace syncer {
+
+bool IsExplicitPassphrase(PassphraseType type) {
+  return type == PassphraseType::CUSTOM_PASSPHRASE ||
+         type == PassphraseType::FROZEN_IMPLICIT_PASSPHRASE;
+}
+
+}  // namespace syncer