Move definition of PasswordType enum to a separate header.

components/sync/engine/sync_string_conversions.h

 // Copyright 2012 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_ENGINE_SYNC_STRING_CONVERSIONS_H_
 #define COMPONENTS_SYNC_ENGINE_SYNC_STRING_CONVERSIONS_H_
 
 #include "components/sync/core/connection_status.h"
 #include "components/sync/core/sync_encryption_handler.h"
 
 namespace syncer {
 
+enum class PassphraseType;
+
 const char* ConnectionStatusToString(ConnectionStatus status);
 
 // Returns the string representation of a PassphraseRequiredReason value.
 const char* PassphraseRequiredReasonToString(PassphraseRequiredReason reason);
 
 const char* PassphraseTypeToString(PassphraseType type);
 
 const char* BootstrapTokenTypeToString(BootstrapTokenType type);
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_ENGINE_SYNC_STRING_CONVERSIONS_H_