Do not reschedule all alarms when adding a new alarm

chrome/browser/extensions/api/alarms/alarm_manager.h

 // Copyright (c) 2012 The Chromium 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 CHROME_BROWSER_EXTENSIONS_API_ALARMS_ALARM_MANAGER_H__
 #define CHROME_BROWSER_EXTENSIONS_API_ALARMS_ALARM_MANAGER_H__
 
 #include <map>
 #include <queue>
 #include <string>
@@ skipping 166 matching lines @@
 
   // Internal helper to add an alarm and start the timer with the given delay.
   void AddAlarmImpl(const std::string& extension_id,
                     const Alarm& alarm);
 
   // Syncs our alarm data for the given extension to/from the state storage.
   void WriteToStorage(const std::string& extension_id);
   void ReadFromStorage(const std::string& extension_id,
                        scoped_ptr<base::Value> value);
 
+  // Set the timer to go off at the specified |time|, and set |next_poll_time|
+  // appropriately.
+  void SetNextPollTime(const base::Time& time);
+
   // Schedules the next poll of alarms for when the next soonest alarm runs,
   // but not more often than the minimum granularity of all alarms.
   void ScheduleNextPoll();
 
   // Polls the alarms, running any that have elapsed. After running them and
   // rescheduling repeating alarms, schedule the next poll.
   void PollAlarms();
 
   // Executes |action| for given extension, making sure that the extension's
   // alarm data has been synced from the storage.
@@ skipping 22 matching lines @@
   // Invariant: None of the AlarmLists are empty.
   AlarmMap alarms_;
 
   // A map of actions waiting for alarm data to be synced from storage, per
   // extension.
   ReadyMap ready_actions_;
 
   // The previous time that alarms were run.
   base::Time last_poll_time_;
 
-  // Next poll's time. Used only by unit tests.
-  base::Time test_next_poll_time_;
+  // Next poll's time.
+  base::Time next_poll_time_;
 
   DISALLOW_COPY_AND_ASSIGN(AlarmManager);
 };
 
 }  //  namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_ALARMS_ALARM_MANAGER_H__