AU: Throttle notifications based on progress; still notify if slow progress.

update_attempter.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_UPDATE_ATTEMPTER_H__
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_UPDATE_ATTEMPTER_H__
 
 #include <time.h>
 
 #include <tr1/memory>
 #include <string>
 #include <vector>
 
 #include <glib.h>
 
+#include "base/time.h"
 #include "update_engine/action_processor.h"
 #include "update_engine/download_action.h"
 #include "update_engine/omaha_request_params.h"
 #include "update_engine/omaha_response_handler_action.h"
 
 class MetricsLibraryInterface;
 struct UpdateEngineService;
 
 namespace chromeos_update_engine {
 
@@ skipping 93 matching lines @@
   // timeout sources.
   void CleanupPriorityManagement();
 
   // The process priority timeout source callback increases the
   // current priority by one step (low goes to normal, normal goes to
   // high). Returns true if the callback must be invoked again after a
   // timeout, or false if GLib can destroy this timeout source.
   static gboolean StaticManagePriorityCallback(gpointer data);
   bool ManagePriorityCallback();
 
-  struct timespec last_notify_time_;
+  // Last status notification timestamp used for throttling. Use
+  // monotonic TimeTicks to ensure that notifications are sent even if
+  // the system clock is set back in the middle of an update.
+  base::TimeTicks last_notify_time_;
 
   std::vector<std::tr1::shared_ptr<AbstractAction> > actions_;
   ActionProcessor processor_;
 
   // If non-null, this UpdateAttempter will send status updates over this
   // dbus service.
   UpdateEngineService* dbus_service_;
 
   // pointer to the OmahaResponseHandlerAction in the actions_ vector;
   std::tr1::shared_ptr<OmahaResponseHandlerAction> response_handler_action_;
@@ skipping 26 matching lines @@
 
   // Device paramaters common to all Omaha requests.
   OmahaRequestDeviceParams omaha_request_params_;
 
   DISALLOW_COPY_AND_ASSIGN(UpdateAttempter);
 };
 
 }  // namespace chromeos_update_engine
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_UPDATE_ATTEMPTER_H__