update_engine: Refresh device policy when it is updated.

The session manager emits a signal whenever the device policy is
updated. This patch makes update_engine listen for that signal and
reload the device policy.

BUG=chromium:423037
TEST=deployed update_engine and checked the policy is refreshed.

Change-Id: I71dd7047e53d49f3402e1f9f4a67ec8cbd3739d3
Reviewed-on: https://chromium-review.googlesource.com/235884
Trybot-Ready: Alex Deymo <deymo@chromium.org>
Reviewed-by: Alex Deymo <deymo@chromium.org>
Commit-Queue: Alex Deymo <deymo@chromium.org>
Tested-by: Alex Deymo <deymo@chromium.org>
diff --git a/update_manager/real_shill_provider.h b/update_manager/real_shill_provider.h
index 1cceadf..5b50bf4 100644
--- a/update_manager/real_shill_provider.h
+++ b/update_manager/real_shill_provider.h
@@ -67,7 +67,7 @@
   bool ProcessDefaultService(GValue* value);
 
   // A handler for manager PropertyChanged signal, and a static version.
-  void HandlePropertyChanged(DBusGProxy* proxy, const char *name,
+  void HandlePropertyChanged(DBusGProxy* proxy, const char* name,
                              GValue* value);
   static void HandlePropertyChangedStatic(DBusGProxy* proxy, const char* name,
                                           GValue* value, void* data);