Move definition of PasswordType enum to a separate header.

components/sync/base/passphrase_type.h

Index: components/sync/base/passphrase_type.h
diff --git a/components/sync/base/passphrase_type.h b/components/sync/base/passphrase_type.h
new file mode 100644
index 0000000000000000000000000000000000000000..bde6b0783af533473d9048086556ae43b8887344
--- /dev/null
+++ b/components/sync/base/passphrase_type.h
@@ -0,0 +1,26 @@
+// 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 COMPONENTS_SYNC_BASE_PASSPHRASE_TYPE_H_
+#define COMPONENTS_SYNC_BASE_PASSPHRASE_TYPE_H_
+
+namespace syncer {
+
+// The different states for the encryption passphrase. These control if and how
+// the user should be prompted for a decryption passphrase.
+// Do not re-order or delete these entries; they are used in a UMA histogram.
+// Please edit SyncPassphraseType in histograms.xml if a value is added.
+enum class PassphraseType {
+  IMPLICIT_PASSPHRASE = 0,         // GAIA-based passphrase (deprecated).
+  KEYSTORE_PASSPHRASE = 1,         // Keystore passphrase.
+  FROZEN_IMPLICIT_PASSPHRASE = 2,  // Frozen GAIA passphrase.
+  CUSTOM_PASSPHRASE = 3,           // User-provided passphrase.
+  PASSPHRASE_TYPE_SIZE,            // The size of this enum; keep last.
+};
+
+bool IsExplicitPassphrase(PassphraseType type);
+
+}  // namespace syncer
+
+#endif  // COMPONENTS_SYNC_BASE_PASSPHRASE_TYPE_H_