Narrow down to one generic error per action.

This way if we miss a spot for returning a more specific error code,
we'll at least know which action failed.

BUG=560
TEST=unit tests, gmerged and confirmed that the PostinstallRunner action
still fails...

Review URL: http://codereview.chromium.org/2819059
diff --git a/update_attempter.h b/update_attempter.h
index e84c479..269edec 100644
--- a/update_attempter.h
+++ b/update_attempter.h
@@ -90,7 +90,7 @@
 
   // Creates an error event object in |error_event_| to be included in
   // an OmahaRequestAction once the current action processor is done.
-  void CreatePendingErrorEvent(ActionExitCode code);
+  void CreatePendingErrorEvent(AbstractAction* action, ActionExitCode code);
 
   // If there's a pending error event allocated in |error_event_|,
   // schedules an OmahaRequestAction with that event in the current