Support in update_engine for the crosh autest "-scheduled" option.

This is needed to enable manual testing of scattering feature on
MP-signed images.

BUG=chromium-os:32289
TEST=update_engine_client works as expected on zgb when passing
     autest and autest-scatter to omaha_url.
Change-Id: Ib3d3e70f2e87632b6a61c7e5cd45791210c12c99
Reviewed-on: https://gerrit.chromium.org/gerrit/27005
Reviewed-by: Gilad Arnold <garnold@chromium.org>
Reviewed-by: Jay Srinivasan <jaysri@chromium.org>
Tested-by: Jay Srinivasan <jaysri@chromium.org>
Commit-Ready: Jay Srinivasan <jaysri@chromium.org>
diff --git a/update_attempter.h b/update_attempter.h
index 7a1855f..77af499 100644
--- a/update_attempter.h
+++ b/update_attempter.h
@@ -133,10 +133,12 @@
     update_check_scheduler_ = scheduler;
   }
 
-  // This is the D-Bus service entry point for going through an
+  // This is the internal entry point for going through an
   // update. If the current status is idle invokes Update.
+  // This is called by the DBus implementation.
   void CheckForUpdate(const std::string& app_version,
-                      const std::string& omaha_url);
+                      const std::string& omaha_url,
+                      bool is_user_initiated);
 
   // Initiates a reboot if the current state is
   // UPDATED_NEED_REBOOT. Returns true on sucess, false otherwise.