extensions/browser/api/alarms/alarm_manager.cc - chromium/src - Git at Google

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

 #include <stddef.h>

 #include <utility>

 #include "base/bind.h"
 #include "base/json/json_writer.h"
 #include "base/lazy_instance.h"
 #include "base/message_loop/message_loop.h"
 #include "base/time/clock.h"
 #include "base/time/default_clock.h"
 #include "base/time/time.h"
 #include "base/value_conversions.h"
 #include "base/values.h"
 #include "extensions/browser/event_router.h"
 #include "extensions/browser/extension_registry.h"
 #include "extensions/browser/extension_system.h"
 #include "extensions/browser/state_store.h"
 #include "extensions/common/api/alarms.h"

 namespace extensions {

 namespace alarms = api::alarms;

 namespace {

 // A list of alarms that this extension has set.
 const char kRegisteredAlarms[] = "alarms";
 const char kAlarmGranularity[] = "granularity";

 // The minimum period between polling for alarms to run.
 const base::TimeDelta kDefaultMinPollPeriod() {
   return base::TimeDelta::FromDays(1);
 }

 class DefaultAlarmDelegate : public AlarmManager::Delegate {
  public:
   explicit DefaultAlarmDelegate(content::BrowserContext* context)
       : browser_context_(context) {}
   ~DefaultAlarmDelegate() override {}

   void OnAlarm(const std::string& extension_id, const Alarm& alarm) override {
     std::unique_ptr<base::ListValue> args(new base::ListValue());
     args->Append(alarm.js_alarm->ToValue());
     std::unique_ptr<Event> event(new Event(
         events::ALARMS_ON_ALARM, alarms::OnAlarm::kEventName, std::move(args)));
     EventRouter::Get(browser_context_)
         ->DispatchEventToExtension(extension_id, std::move(event));
   }

  private:
   content::BrowserContext* browser_context_;
 };

 // Creates a TimeDelta from a delay as specified in the API.
 base::TimeDelta TimeDeltaFromDelay(double delay_in_minutes) {
   return base::TimeDelta::FromMicroseconds(delay_in_minutes *
                                            base::Time::kMicrosecondsPerMinute);
 }

 std::vector<Alarm> AlarmsFromValue(const base::ListValue* list) {
   std::vector<Alarm> alarms;
   for (size_t i = 0; i < list->GetSize(); ++i) {
     const base::DictionaryValue* alarm_dict = NULL;
     Alarm alarm;
     if (list->GetDictionary(i, &alarm_dict) &&
         alarms::Alarm::Populate(*alarm_dict, alarm.js_alarm.get())) {
       const base::Value* time_value = NULL;
       if (alarm_dict->Get(kAlarmGranularity, &time_value))
         base::GetValueAsTimeDelta(*time_value, &alarm.granularity);
       alarms.push_back(alarm);
     }
   }
   return alarms;
 }

 std::unique_ptr<base::ListValue> AlarmsToValue(
     const std::vector<Alarm>& alarms) {
   std::unique_ptr<base::ListValue> list(new base::ListValue());
   for (size_t i = 0; i < alarms.size(); ++i) {
     std::unique_ptr<base::DictionaryValue> alarm =
         alarms[i].js_alarm->ToValue();
     alarm->Set(kAlarmGranularity,
                base::CreateTimeDeltaValue(alarms[i].granularity));
     list->Append(std::move(alarm));
   }
   return list;
 }

 }  // namespace

 // AlarmManager

 AlarmManager::AlarmManager(content::BrowserContext* context)
     : browser_context_(context),
       clock_(new base::DefaultClock()),
       delegate_(new DefaultAlarmDelegate(context)),
       extension_registry_observer_(this) {
   extension_registry_observer_.Add(ExtensionRegistry::Get(browser_context_));

   StateStore* storage = ExtensionSystem::Get(browser_context_)->state_store();
   if (storage)
     storage->RegisterKey(kRegisteredAlarms);
 }

 AlarmManager::~AlarmManager() {
 }

 void AlarmManager::AddAlarm(const std::string& extension_id,
                             const Alarm& alarm,
                             const AddAlarmCallback& callback) {
   RunWhenReady(extension_id, base::Bind(&AlarmManager::AddAlarmWhenReady,
                                         AsWeakPtr(), alarm, callback));
 }

 void AlarmManager::GetAlarm(const std::string& extension_id,
                             const std::string& name,
                             const GetAlarmCallback& callback) {
   RunWhenReady(extension_id, base::Bind(&AlarmManager::GetAlarmWhenReady,
                                         AsWeakPtr(), name, callback));
 }

 void AlarmManager::GetAllAlarms(const std::string& extension_id,
                                 const GetAllAlarmsCallback& callback) {
   RunWhenReady(extension_id, base::Bind(&AlarmManager::GetAllAlarmsWhenReady,
                                         AsWeakPtr(), callback));
 }

 void AlarmManager::RemoveAlarm(const std::string& extension_id,
                                const std::string& name,
                                const RemoveAlarmCallback& callback) {
   RunWhenReady(extension_id, base::Bind(&AlarmManager::RemoveAlarmWhenReady,
                                         AsWeakPtr(), name, callback));
 }

 void AlarmManager::RemoveAllAlarms(const std::string& extension_id,
                                    const RemoveAllAlarmsCallback& callback) {
   RunWhenReady(extension_id, base::Bind(&AlarmManager::RemoveAllAlarmsWhenReady,
                                         AsWeakPtr(), callback));
 }

 void AlarmManager::AddAlarmWhenReady(const Alarm& alarm,
                                      const AddAlarmCallback& callback,
                                      const std::string& extension_id) {
   AddAlarmImpl(extension_id, alarm);
   WriteToStorage(extension_id);
   callback.Run();
 }

 void AlarmManager::GetAlarmWhenReady(const std::string& name,
                                      const GetAlarmCallback& callback,
                                      const std::string& extension_id) {
   AlarmIterator it = GetAlarmIterator(extension_id, name);
   callback.Run(it.first != alarms_.end() ? &*it.second : NULL);
 }

 void AlarmManager::GetAllAlarmsWhenReady(const GetAllAlarmsCallback& callback,
                                          const std::string& extension_id) {
   AlarmMap::iterator list = alarms_.find(extension_id);
   callback.Run(list != alarms_.end() ? &list->second : NULL);
 }

 void AlarmManager::RemoveAlarmWhenReady(const std::string& name,
                                         const RemoveAlarmCallback& callback,
                                         const std::string& extension_id) {
   AlarmIterator it = GetAlarmIterator(extension_id, name);
   if (it.first == alarms_.end()) {
     callback.Run(false);
     return;
   }

   RemoveAlarmIterator(it);
   WriteToStorage(extension_id);
   callback.Run(true);
 }

 void AlarmManager::RemoveAllAlarmsWhenReady(
     const RemoveAllAlarmsCallback& callback,
     const std::string& extension_id) {
   AlarmMap::iterator list = alarms_.find(extension_id);
   if (list != alarms_.end()) {
     // Note: I'm using indices rather than iterators here because
     // RemoveAlarmIterator will delete the list when it becomes empty.
     for (size_t i = 0, size = list->second.size(); i < size; ++i)
       RemoveAlarmIterator(AlarmIterator(list, list->second.begin()));

     CHECK(alarms_.find(extension_id) == alarms_.end());
     WriteToStorage(extension_id);
   }
   callback.Run();
 }

 AlarmManager::AlarmIterator AlarmManager::GetAlarmIterator(
     const std::string& extension_id,
     const std::string& name) {
   AlarmMap::iterator list = alarms_.find(extension_id);
   if (list == alarms_.end())
     return make_pair(alarms_.end(), AlarmList::iterator());

   for (AlarmList::iterator it = list->second.begin(); it != list->second.end();
        ++it) {
     if (it->js_alarm->name == name)
       return make_pair(list, it);
   }

   return make_pair(alarms_.end(), AlarmList::iterator());
 }

 void AlarmManager::SetClockForTesting(base::Clock* clock) {
   clock_.reset(clock);
 }

 static base::LazyInstance<BrowserContextKeyedAPIFactory<AlarmManager>>
     g_factory = LAZY_INSTANCE_INITIALIZER;

 // static
 BrowserContextKeyedAPIFactory<AlarmManager>*
 AlarmManager::GetFactoryInstance() {
   return g_factory.Pointer();
 }

 // static
 AlarmManager* AlarmManager::Get(content::BrowserContext* browser_context) {
   return BrowserContextKeyedAPIFactory<AlarmManager>::Get(browser_context);
 }

 void AlarmManager::RemoveAlarmIterator(const AlarmIterator& iter) {
   AlarmList& list = iter.first->second;
   list.erase(iter.second);
   if (list.empty())
     alarms_.erase(iter.first);

   // Cancel the timer if there are no more alarms.
   // We don't need to reschedule the poll otherwise, because in
   // the worst case we would just poll one extra time.
   if (alarms_.empty()) {
     timer_.Stop();
     next_poll_time_ = base::Time();
   }
 }

 void AlarmManager::OnAlarm(AlarmIterator it) {
   CHECK(it.first != alarms_.end());
   Alarm& alarm = *it.second;
   std::string extension_id_copy(it.first->first);
   delegate_->OnAlarm(extension_id_copy, alarm);

   // Update our scheduled time for the next alarm.
   if (double* period_in_minutes = alarm.js_alarm->period_in_minutes.get()) {
     // Get the timer's delay in JS time (i.e., convert it from minutes to
     // milliseconds).
     double period_in_js_time = *period_in_minutes *
                                base::Time::kMicrosecondsPerMinute /
                                base::Time::kMicrosecondsPerMillisecond;
     // Find out how many periods have transpired since the alarm last went off
     // (it's possible that we missed some).
     int transpired_periods =
         (last_poll_time_.ToJsTime() - alarm.js_alarm->scheduled_time) /
         period_in_js_time;
     // Schedule the alarm for the next period that is in-line with the original
     // scheduling.
     alarm.js_alarm->scheduled_time +=
         period_in_js_time * (transpired_periods + 1);
   } else {
     RemoveAlarmIterator(it);
   }
   WriteToStorage(extension_id_copy);
 }

 void AlarmManager::AddAlarmImpl(const std::string& extension_id,
                                 const Alarm& alarm) {
   // Override any old alarm with the same name.
   AlarmIterator old_alarm =
       GetAlarmIterator(extension_id, alarm.js_alarm->name);
   if (old_alarm.first != alarms_.end())
     RemoveAlarmIterator(old_alarm);

   alarms_[extension_id].push_back(alarm);
   base::Time alarm_time =
       base::Time::FromJsTime(alarm.js_alarm->scheduled_time);
   if (next_poll_time_.is_null() || alarm_time < next_poll_time_)
     SetNextPollTime(alarm_time);
 }

 void AlarmManager::WriteToStorage(const std::string& extension_id) {
   StateStore* storage = ExtensionSystem::Get(browser_context_)->state_store();
   if (!storage)
     return;

   std::unique_ptr<base::Value> alarms;
   AlarmMap::iterator list = alarms_.find(extension_id);
   if (list != alarms_.end())
     alarms.reset(AlarmsToValue(list->second).release());
   else
     alarms.reset(AlarmsToValue(std::vector<Alarm>()).release());
   storage->SetExtensionValue(extension_id, kRegisteredAlarms,
                              std::move(alarms));
 }

 void AlarmManager::ReadFromStorage(const std::string& extension_id,
                                    std::unique_ptr<base::Value> value) {
   base::ListValue* list = NULL;
   if (value.get() && value->GetAsList(&list)) {
     std::vector<Alarm> alarm_states = AlarmsFromValue(list);
     for (size_t i = 0; i < alarm_states.size(); ++i)
       AddAlarmImpl(extension_id, alarm_states[i]);
   }

   ReadyQueue& extension_ready_queue = ready_actions_[extension_id];
   while (!extension_ready_queue.empty()) {
     extension_ready_queue.front().Run(extension_id);
     extension_ready_queue.pop();
   }
   ready_actions_.erase(extension_id);
 }

 void AlarmManager::SetNextPollTime(const base::Time& time) {
   next_poll_time_ = time;
   timer_.Start(FROM_HERE,
                std::max(base::TimeDelta::FromSeconds(0), time - clock_->Now()),
                this, &AlarmManager::PollAlarms);
 }

 void AlarmManager::ScheduleNextPoll() {
   // If there are no alarms, stop the timer.
   if (alarms_.empty()) {
     timer_.Stop();
     next_poll_time_ = base::Time();
     return;
   }

   // Find the soonest alarm that is scheduled to run and the smallest
   // granularity of any alarm.
   // alarms_ guarantees that none of its contained lists are empty.
   base::Time soonest_alarm_time = base::Time::FromJsTime(
       alarms_.begin()->second.begin()->js_alarm->scheduled_time);
   base::TimeDelta min_granularity = kDefaultMinPollPeriod();
   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 - last_poll_time_;
       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;
     }
   }

   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;

   // Schedule the poll.
   SetNextPollTime(next_poll);
 }

 void AlarmManager::PollAlarms() {
   last_poll_time_ = clock_->Now();

   // Run any alarms scheduled in the past. OnAlarm uses vector::erase to remove
   // elements from the AlarmList, and map::erase to remove AlarmLists from the
   // AlarmMap.
   for (AlarmMap::iterator m_it = alarms_.begin(), m_end = alarms_.end();
        m_it != m_end;) {
     AlarmMap::iterator cur_extension = m_it++;

     // Iterate (a) backwards so that removing elements doesn't affect
     // upcoming iterations, and (b) with indices so that if the last
     // iteration destroys the AlarmList, I'm not about to use the end
     // iterator that the destruction invalidates.
     for (size_t i = cur_extension->second.size(); i > 0; --i) {
       AlarmList::iterator cur_alarm = cur_extension->second.begin() + i - 1;
       if (base::Time::FromJsTime(cur_alarm->js_alarm->scheduled_time) <=
           last_poll_time_) {
         OnAlarm(make_pair(cur_extension, cur_alarm));
       }
     }
   }

   ScheduleNextPoll();
 }

 static void RemoveAllOnUninstallCallback() {
 }

 void AlarmManager::RunWhenReady(const std::string& extension_id,
                                 const ReadyAction& action) {
   ReadyMap::iterator it = ready_actions_.find(extension_id);

   if (it == ready_actions_.end())
     action.Run(extension_id);
   else
     it->second.push(action);
 }

 void AlarmManager::OnExtensionLoaded(content::BrowserContext* browser_context,
                                      const Extension* extension) {
   StateStore* storage = ExtensionSystem::Get(browser_context_)->state_store();
   if (storage) {
     ready_actions_.insert(ReadyMap::value_type(extension->id(), ReadyQueue()));
     storage->GetExtensionValue(extension->id(), kRegisteredAlarms,
                                base::Bind(&AlarmManager::ReadFromStorage,
                                           AsWeakPtr(), extension->id()));
   }
 }

 void AlarmManager::OnExtensionUninstalled(
     content::BrowserContext* browser_context,
     const Extension* extension,
     extensions::UninstallReason reason) {
   RemoveAllAlarms(extension->id(), base::Bind(RemoveAllOnUninstallCallback));
 }

 // AlarmManager::Alarm

 Alarm::Alarm() : js_alarm(new alarms::Alarm()) {
 }

 Alarm::Alarm(const std::string& name,
              const alarms::AlarmCreateInfo& create_info,
              base::TimeDelta min_granularity,
              base::Time now)
     : js_alarm(new alarms::Alarm()) {
   js_alarm->name = name;
   minimum_granularity = min_granularity;

   if (create_info.when.get()) {
     // Absolute scheduling.
     js_alarm->scheduled_time = *create_info.when;
     granularity = base::Time::FromJsTime(js_alarm->scheduled_time) - now;
   } else {
     // Relative scheduling.
     double* delay_in_minutes = create_info.delay_in_minutes.get();
     if (delay_in_minutes == NULL)
       delay_in_minutes = create_info.period_in_minutes.get();
     CHECK(delay_in_minutes != NULL)
         << "ValidateAlarmCreateInfo in alarms_api.cc should have "
         << "prevented this call.";
     base::TimeDelta delay = TimeDeltaFromDelay(*delay_in_minutes);
     js_alarm->scheduled_time = (now + delay).ToJsTime();
     granularity = delay;
   }

   if (granularity < min_granularity)
     granularity = min_granularity;

   // Check for repetition.
   if (create_info.period_in_minutes.get()) {
     js_alarm->period_in_minutes.reset(
         new double(*create_info.period_in_minutes));
   }
 }

 Alarm::Alarm(const Alarm& other) = default;

 Alarm::~Alarm() {
 }

 }  // namespace extensions
	// 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 "extensions/browser/api/alarms/alarm_manager.h"

	#include <stddef.h>

	#include <utility>

	#include "base/bind.h"
	#include "base/json/json_writer.h"
	#include "base/lazy_instance.h"
	#include "base/message_loop/message_loop.h"
	#include "base/time/clock.h"
	#include "base/time/default_clock.h"
	#include "base/time/time.h"
	#include "base/value_conversions.h"
	#include "base/values.h"
	#include "extensions/browser/event_router.h"
	#include "extensions/browser/extension_registry.h"
	#include "extensions/browser/extension_system.h"
	#include "extensions/browser/state_store.h"
	#include "extensions/common/api/alarms.h"

	namespace extensions {

	namespace alarms = api::alarms;

	namespace {

	// A list of alarms that this extension has set.
	const char kRegisteredAlarms[] = "alarms";
	const char kAlarmGranularity[] = "granularity";

	// The minimum period between polling for alarms to run.
	const base::TimeDelta kDefaultMinPollPeriod() {
	return base::TimeDelta::FromDays(1);
	}

	class DefaultAlarmDelegate : public AlarmManager::Delegate {
	public:
	explicit DefaultAlarmDelegate(content::BrowserContext* context)
	: browser_context_(context) {}
	~DefaultAlarmDelegate() override {}

	void OnAlarm(const std::string& extension_id, const Alarm& alarm) override {
	std::unique_ptr<base::ListValue> args(new base::ListValue());
	args->Append(alarm.js_alarm->ToValue());
	std::unique_ptr<Event> event(new Event(
	events::ALARMS_ON_ALARM, alarms::OnAlarm::kEventName, std::move(args)));
	EventRouter::Get(browser_context_)
	->DispatchEventToExtension(extension_id, std::move(event));
	}

	private:
	content::BrowserContext* browser_context_;
	};

	// Creates a TimeDelta from a delay as specified in the API.
	base::TimeDelta TimeDeltaFromDelay(double delay_in_minutes) {
	return base::TimeDelta::FromMicroseconds(delay_in_minutes *
	base::Time::kMicrosecondsPerMinute);
	}

	std::vector<Alarm> AlarmsFromValue(const base::ListValue* list) {
	std::vector<Alarm> alarms;
	for (size_t i = 0; i < list->GetSize(); ++i) {
	const base::DictionaryValue* alarm_dict = NULL;
	Alarm alarm;
	if (list->GetDictionary(i, &alarm_dict) &&
	alarms::Alarm::Populate(*alarm_dict, alarm.js_alarm.get())) {
	const base::Value* time_value = NULL;
	if (alarm_dict->Get(kAlarmGranularity, &time_value))
	base::GetValueAsTimeDelta(*time_value, &alarm.granularity);
	alarms.push_back(alarm);
	}
	}
	return alarms;
	}

	std::unique_ptr<base::ListValue> AlarmsToValue(
	const std::vector<Alarm>& alarms) {
	std::unique_ptr<base::ListValue> list(new base::ListValue());
	for (size_t i = 0; i < alarms.size(); ++i) {
	std::unique_ptr<base::DictionaryValue> alarm =
	alarms[i].js_alarm->ToValue();
	alarm->Set(kAlarmGranularity,
	base::CreateTimeDeltaValue(alarms[i].granularity));
	list->Append(std::move(alarm));
	}
	return list;
	}

	} // namespace

	// AlarmManager

	AlarmManager::AlarmManager(content::BrowserContext* context)
	: browser_context_(context),
	clock_(new base::DefaultClock()),
	delegate_(new DefaultAlarmDelegate(context)),
	extension_registry_observer_(this) {
	extension_registry_observer_.Add(ExtensionRegistry::Get(browser_context_));

	StateStore* storage = ExtensionSystem::Get(browser_context_)->state_store();
	if (storage)
	storage->RegisterKey(kRegisteredAlarms);
	}

	AlarmManager::~AlarmManager() {
	}

	void AlarmManager::AddAlarm(const std::string& extension_id,
	const Alarm& alarm,
	const AddAlarmCallback& callback) {
	RunWhenReady(extension_id, base::Bind(&AlarmManager::AddAlarmWhenReady,
	AsWeakPtr(), alarm, callback));
	}

	void AlarmManager::GetAlarm(const std::string& extension_id,
	const std::string& name,
	const GetAlarmCallback& callback) {
	RunWhenReady(extension_id, base::Bind(&AlarmManager::GetAlarmWhenReady,
	AsWeakPtr(), name, callback));
	}

	void AlarmManager::GetAllAlarms(const std::string& extension_id,
	const GetAllAlarmsCallback& callback) {
	RunWhenReady(extension_id, base::Bind(&AlarmManager::GetAllAlarmsWhenReady,
	AsWeakPtr(), callback));
	}

	void AlarmManager::RemoveAlarm(const std::string& extension_id,
	const std::string& name,
	const RemoveAlarmCallback& callback) {
	RunWhenReady(extension_id, base::Bind(&AlarmManager::RemoveAlarmWhenReady,
	AsWeakPtr(), name, callback));
	}

	void AlarmManager::RemoveAllAlarms(const std::string& extension_id,
	const RemoveAllAlarmsCallback& callback) {
	RunWhenReady(extension_id, base::Bind(&AlarmManager::RemoveAllAlarmsWhenReady,
	AsWeakPtr(), callback));
	}

	void AlarmManager::AddAlarmWhenReady(const Alarm& alarm,
	const AddAlarmCallback& callback,
	const std::string& extension_id) {
	AddAlarmImpl(extension_id, alarm);
	WriteToStorage(extension_id);
	callback.Run();
	}

	void AlarmManager::GetAlarmWhenReady(const std::string& name,
	const GetAlarmCallback& callback,
	const std::string& extension_id) {
	AlarmIterator it = GetAlarmIterator(extension_id, name);
	callback.Run(it.first != alarms_.end() ? &*it.second : NULL);
	}

	void AlarmManager::GetAllAlarmsWhenReady(const GetAllAlarmsCallback& callback,
	const std::string& extension_id) {
	AlarmMap::iterator list = alarms_.find(extension_id);
	callback.Run(list != alarms_.end() ? &list->second : NULL);
	}

	void AlarmManager::RemoveAlarmWhenReady(const std::string& name,
	const RemoveAlarmCallback& callback,
	const std::string& extension_id) {
	AlarmIterator it = GetAlarmIterator(extension_id, name);
	if (it.first == alarms_.end()) {
	callback.Run(false);
	return;
	}

	RemoveAlarmIterator(it);
	WriteToStorage(extension_id);
	callback.Run(true);
	}

	void AlarmManager::RemoveAllAlarmsWhenReady(
	const RemoveAllAlarmsCallback& callback,
	const std::string& extension_id) {
	AlarmMap::iterator list = alarms_.find(extension_id);
	if (list != alarms_.end()) {
	// Note: I'm using indices rather than iterators here because
	// RemoveAlarmIterator will delete the list when it becomes empty.
	for (size_t i = 0, size = list->second.size(); i < size; ++i)
	RemoveAlarmIterator(AlarmIterator(list, list->second.begin()));

	CHECK(alarms_.find(extension_id) == alarms_.end());
	WriteToStorage(extension_id);
	}
	callback.Run();
	}

	AlarmManager::AlarmIterator AlarmManager::GetAlarmIterator(
	const std::string& extension_id,
	const std::string& name) {
	AlarmMap::iterator list = alarms_.find(extension_id);
	if (list == alarms_.end())
	return make_pair(alarms_.end(), AlarmList::iterator());

	for (AlarmList::iterator it = list->second.begin(); it != list->second.end();
	++it) {
	if (it->js_alarm->name == name)
	return make_pair(list, it);
	}

	return make_pair(alarms_.end(), AlarmList::iterator());
	}

	void AlarmManager::SetClockForTesting(base::Clock* clock) {
	clock_.reset(clock);
	}

	static base::LazyInstance<BrowserContextKeyedAPIFactory<AlarmManager>>
	g_factory = LAZY_INSTANCE_INITIALIZER;

	// static
	BrowserContextKeyedAPIFactory<AlarmManager>*
	AlarmManager::GetFactoryInstance() {
	return g_factory.Pointer();
	}

	// static
	AlarmManager* AlarmManager::Get(content::BrowserContext* browser_context) {
	return BrowserContextKeyedAPIFactory<AlarmManager>::Get(browser_context);
	}

	void AlarmManager::RemoveAlarmIterator(const AlarmIterator& iter) {
	AlarmList& list = iter.first->second;
	list.erase(iter.second);
	if (list.empty())
	alarms_.erase(iter.first);

	// Cancel the timer if there are no more alarms.
	// We don't need to reschedule the poll otherwise, because in
	// the worst case we would just poll one extra time.
	if (alarms_.empty()) {
	timer_.Stop();
	next_poll_time_ = base::Time();
	}
	}

	void AlarmManager::OnAlarm(AlarmIterator it) {
	CHECK(it.first != alarms_.end());
	Alarm& alarm = *it.second;
	std::string extension_id_copy(it.first->first);
	delegate_->OnAlarm(extension_id_copy, alarm);

	// Update our scheduled time for the next alarm.
	if (double* period_in_minutes = alarm.js_alarm->period_in_minutes.get()) {
	// Get the timer's delay in JS time (i.e., convert it from minutes to
	// milliseconds).
	double period_in_js_time = period_in_minutes
	base::Time::kMicrosecondsPerMinute /
	base::Time::kMicrosecondsPerMillisecond;
	// Find out how many periods have transpired since the alarm last went off
	// (it's possible that we missed some).
	int transpired_periods =
	(last_poll_time_.ToJsTime() - alarm.js_alarm->scheduled_time) /
	period_in_js_time;
	// Schedule the alarm for the next period that is in-line with the original
	// scheduling.
	alarm.js_alarm->scheduled_time +=
	period_in_js_time * (transpired_periods + 1);
	} else {
	RemoveAlarmIterator(it);
	}
	WriteToStorage(extension_id_copy);
	}

	void AlarmManager::AddAlarmImpl(const std::string& extension_id,
	const Alarm& alarm) {
	// Override any old alarm with the same name.
	AlarmIterator old_alarm =
	GetAlarmIterator(extension_id, alarm.js_alarm->name);
	if (old_alarm.first != alarms_.end())
	RemoveAlarmIterator(old_alarm);

	alarms_[extension_id].push_back(alarm);
	base::Time alarm_time =
	base::Time::FromJsTime(alarm.js_alarm->scheduled_time);
	if (next_poll_time_.is_null() \|\| alarm_time < next_poll_time_)
	SetNextPollTime(alarm_time);
	}

	void AlarmManager::WriteToStorage(const std::string& extension_id) {
	StateStore* storage = ExtensionSystem::Get(browser_context_)->state_store();
	if (!storage)
	return;

	std::unique_ptr<base::Value> alarms;
	AlarmMap::iterator list = alarms_.find(extension_id);
	if (list != alarms_.end())
	alarms.reset(AlarmsToValue(list->second).release());
	else
	alarms.reset(AlarmsToValue(std::vector<Alarm>()).release());
	storage->SetExtensionValue(extension_id, kRegisteredAlarms,
	std::move(alarms));
	}

	void AlarmManager::ReadFromStorage(const std::string& extension_id,
	std::unique_ptr<base::Value> value) {
	base::ListValue* list = NULL;
	if (value.get() && value->GetAsList(&list)) {
	std::vector<Alarm> alarm_states = AlarmsFromValue(list);
	for (size_t i = 0; i < alarm_states.size(); ++i)
	AddAlarmImpl(extension_id, alarm_states[i]);
	}

	ReadyQueue& extension_ready_queue = ready_actions_[extension_id];
	while (!extension_ready_queue.empty()) {
	extension_ready_queue.front().Run(extension_id);
	extension_ready_queue.pop();
	}
	ready_actions_.erase(extension_id);
	}

	void AlarmManager::SetNextPollTime(const base::Time& time) {
	next_poll_time_ = time;
	timer_.Start(FROM_HERE,
	std::max(base::TimeDelta::FromSeconds(0), time - clock_->Now()),
	this, &AlarmManager::PollAlarms);
	}

	void AlarmManager::ScheduleNextPoll() {
	// If there are no alarms, stop the timer.
	if (alarms_.empty()) {
	timer_.Stop();
	next_poll_time_ = base::Time();
	return;
	}

	// Find the soonest alarm that is scheduled to run and the smallest
	// granularity of any alarm.
	// alarms_ guarantees that none of its contained lists are empty.
	base::Time soonest_alarm_time = base::Time::FromJsTime(
	alarms_.begin()->second.begin()->js_alarm->scheduled_time);
	base::TimeDelta min_granularity = kDefaultMinPollPeriod();
	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 - last_poll_time_;
	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;
	}
	}

	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;

	// Schedule the poll.
	SetNextPollTime(next_poll);
	}

	void AlarmManager::PollAlarms() {
	last_poll_time_ = clock_->Now();

	// Run any alarms scheduled in the past. OnAlarm uses vector::erase to remove
	// elements from the AlarmList, and map::erase to remove AlarmLists from the
	// AlarmMap.
	for (AlarmMap::iterator m_it = alarms_.begin(), m_end = alarms_.end();
	m_it != m_end;) {
	AlarmMap::iterator cur_extension = m_it++;

	// Iterate (a) backwards so that removing elements doesn't affect
	// upcoming iterations, and (b) with indices so that if the last
	// iteration destroys the AlarmList, I'm not about to use the end
	// iterator that the destruction invalidates.
	for (size_t i = cur_extension->second.size(); i > 0; --i) {
	AlarmList::iterator cur_alarm = cur_extension->second.begin() + i - 1;
	if (base::Time::FromJsTime(cur_alarm->js_alarm->scheduled_time) <=
	last_poll_time_) {
	OnAlarm(make_pair(cur_extension, cur_alarm));
	}
	}
	}

	ScheduleNextPoll();
	}

	static void RemoveAllOnUninstallCallback() {
	}

	void AlarmManager::RunWhenReady(const std::string& extension_id,
	const ReadyAction& action) {
	ReadyMap::iterator it = ready_actions_.find(extension_id);

	if (it == ready_actions_.end())
	action.Run(extension_id);
	else
	it->second.push(action);
	}

	void AlarmManager::OnExtensionLoaded(content::BrowserContext* browser_context,
	const Extension* extension) {
	StateStore* storage = ExtensionSystem::Get(browser_context_)->state_store();
	if (storage) {
	ready_actions_.insert(ReadyMap::value_type(extension->id(), ReadyQueue()));
	storage->GetExtensionValue(extension->id(), kRegisteredAlarms,
	base::Bind(&AlarmManager::ReadFromStorage,
	AsWeakPtr(), extension->id()));
	}
	}

	void AlarmManager::OnExtensionUninstalled(
	content::BrowserContext* browser_context,
	const Extension* extension,
	extensions::UninstallReason reason) {
	RemoveAllAlarms(extension->id(), base::Bind(RemoveAllOnUninstallCallback));
	}

	// AlarmManager::Alarm

	Alarm::Alarm() : js_alarm(new alarms::Alarm()) {
	}

	Alarm::Alarm(const std::string& name,
	const alarms::AlarmCreateInfo& create_info,
	base::TimeDelta min_granularity,
	base::Time now)
	: js_alarm(new alarms::Alarm()) {
	js_alarm->name = name;
	minimum_granularity = min_granularity;

	if (create_info.when.get()) {
	// Absolute scheduling.
	js_alarm->scheduled_time = *create_info.when;
	granularity = base::Time::FromJsTime(js_alarm->scheduled_time) - now;
	} else {
	// Relative scheduling.
	double* delay_in_minutes = create_info.delay_in_minutes.get();
	if (delay_in_minutes == NULL)
	delay_in_minutes = create_info.period_in_minutes.get();
	CHECK(delay_in_minutes != NULL)
	<< "ValidateAlarmCreateInfo in alarms_api.cc should have "
	<< "prevented this call.";
	base::TimeDelta delay = TimeDeltaFromDelay(*delay_in_minutes);
	js_alarm->scheduled_time = (now + delay).ToJsTime();
	granularity = delay;
	}

	if (granularity < min_granularity)
	granularity = min_granularity;

	// Check for repetition.
	if (create_info.period_in_minutes.get()) {
	js_alarm->period_in_minutes.reset(
	new double(*create_info.period_in_minutes));
	}
	}

	Alarm::Alarm(const Alarm& other) = default;

	Alarm::~Alarm() {
	}

	} // namespace extensions