Fix a bug where the minimum granular time for Alarms was not calculated properly.

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 26 matching lines @@
         base::Time now);
   ~Alarm();
 
   linked_ptr<api::alarms::Alarm> js_alarm;
   // The granularity isn't exposed to the extension's javascript, but we poll at
   // least as often as the shortest alarm's granularity.  It's initialized as
   // the relative delay requested in creation, even if creation uses an absolute
   // time.  This will always be at least as large as the min_granularity
   // constructor argument.
   base::TimeDelta granularity;
+  // The minimum granularity is the minimum allowed polling rate. This stops
+  // alarms from polling too often.
+  base::TimeDelta minimum_granularity;
 };
 
 // Manages the currently pending alarms for every extension in a profile.
 // There is one manager per virtual Profile.
 class AlarmManager
     : public ProfileKeyedAPI,
       public content::NotificationObserver,
       public base::SupportsWeakPtr<AlarmManager> {
  public:
   typedef std::vector<Alarm> AlarmList;
@@ skipping 163 matching lines @@
 
   // Next poll's time. Used only by unit tests.
   base::Time test_next_poll_time_;
 
   DISALLOW_COPY_AND_ASSIGN(AlarmManager);
 };
 
 }  //  namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_ALARMS_ALARM_MANAGER_H__