Fix an issue found in https://chromiumcodereview.appspot.com/23205008/

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

 // 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.
 
 #include "chrome/browser/extensions/api/alarms/alarm_manager.h"
 
 #include "base/bind.h"
 #include "base/json/json_writer.h"
 #include "base/lazy_instance.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 310 matching lines @@
   for (AlarmMap::const_iterator m_it = alarms_.begin(), m_end = alarms_.end();
        m_it != m_end; ++m_it) {
     for (AlarmList::const_iterator l_it = m_it->second.begin();
          l_it != m_it->second.end(); ++l_it) {
       base::Time cur_alarm_time =
           base::Time::FromJsTime(l_it->js_alarm->scheduled_time);
       if (cur_alarm_time < soonest_alarm_time)
         soonest_alarm_time = cur_alarm_time;
       if (l_it->granularity < min_granularity)
         min_granularity = l_it->granularity;
-      base::TimeDelta cur_alarm_delta = cur_alarm_time - clock_->Now();
+      base::TimeDelta cur_alarm_delta = cur_alarm_time - last_poll_time_;

[Devlin, 2014/01/17 17:25:04]

Slight tweak from Matt's solution here - I think this should be subtracting
last_poll_time_ instead of clock_->Now(), because that's what we add
min_granularity to below.

+      if (cur_alarm_delta < l_it->minimum_granularity)
+        cur_alarm_delta = l_it->minimum_granularity;
       if (cur_alarm_delta < min_granularity)
         min_granularity = cur_alarm_delta;
-      if (min_granularity < l_it->minimum_granularity)
-        min_granularity = l_it->minimum_granularity;
     }
   }
 
   base::Time next_poll(last_poll_time_ + min_granularity);
   // If the next alarm is more than min_granularity in the future, wait for it.
   // Otherwise, only poll as often as min_granularity.
   // As a special case, if we've never checked for an alarm before
   // (e.g. during startup), let alarms fire asap.
   if (last_poll_time_.is_null() || next_poll < soonest_alarm_time)
     next_poll = soonest_alarm_time;
@@ skipping 115 matching lines @@
   if (create_info.period_in_minutes.get()) {
     js_alarm->period_in_minutes.reset(
         new double(*create_info.period_in_minutes));
   }
 }
 
 Alarm::~Alarm() {
 }
 
 }  // namespace extensions