AU: Provide a D-Bus API for changing the update track.

dbus_service.h

 // Copyright (c) 2010 The Chromium OS 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 CHROMEOS_PLATFORM_UPDATE_ENGINE_DBUS_SERVICE_H__
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_DBUS_SERVICE_H__
 
 #include <inttypes.h>
 #include <dbus/dbus-glib.h>
 #include <dbus/dbus-glib-bindings.h>
@@ skipping 44 matching lines @@
                                           int64_t* last_checked_time,
                                           double* progress,
                                           gchar** current_operation,
                                           gchar** new_version,
                                           int64_t* new_size,
                                           GError **error);
 
 gboolean update_engine_service_reboot_if_needed(UpdateEngineService* self,
                                                 GError **error);
 
+gboolean update_engine_service_set_track(UpdateEngineService* self,
+                                         gchar* track,
+                                         GError **error);
+
 gboolean update_engine_service_emit_status_update(
     UpdateEngineService* self,
     gint64 last_checked_time,
     gdouble progress,
     const gchar* current_operation,
     const gchar* new_version,
     gint64 new_size);
 
 G_END_DECLS
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_DBUS_SERVICE_H__