Unrevert r141537: Add extensions::StateStore and use that instead of

ExtensionPrefs for persisting alarm state to disk.

More to come:
- context menus
- omnibox
- declarative webRequest

TBR=brettw
BUG=123366
TEST=extension alarms are still remembered after chrome restart

Change since last time: Fall back to a FailingValueStore if ValueStoreFrontend
can't open the database.

Review URL: https://chromiumcodereview.appspot.com/10545128

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@141780 0039d316-1c4b-4281-b951-d872f2087c98

15 files changed, 282 insertions, 99 deletions

diff --git a/base/value_conversions.cc b/base/value_conversions.cc
index f4957a4..caf9d72 100644
--- a/base/value_conversions.cc
+++ b/base/value_conversions.cc
@@ -1,10 +1,12 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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 "base/value_conversions.h"
 
 #include "base/file_path.h"
+#include "base/string_number_conversions.h"
+#include "base/time.h"
 #include "base/values.h"
 
 namespace base {
@@ -24,4 +26,21 @@ bool GetValueAsFilePath(const Value& value, FilePath* file_path) {
   return true;
 }
 
+// |Value| does not support 64-bit integers, and doubles do not have enough
+// precision, so we store the 64-bit time value as a string instead.
+StringValue* CreateTimeValue(const Time& time) {
+  std::string string_value = base::Int64ToString(time.ToInternalValue());
+  return new StringValue(string_value);
+}
+
+bool GetValueAsTime(const Value& value, Time* time) {
+  std::string str;
+  int64 int_value;
+  if (!value.GetAsString(&str) || !base::StringToInt64(str, &int_value))
+    return false;
+  if (time)
+    *time = base::Time::FromInternalValue(int_value);
+  return true;
+}
+
 }  // namespace base
diff --git a/base/value_conversions.h b/base/value_conversions.h
index c65e627..7825bb1 100644
--- a/base/value_conversions.h
+++ b/base/value_conversions.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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.
 
@@ -6,7 +6,7 @@
 #define BASE_VALUE_CONVERSIONS_H_
 #pragma once
 
-// This file contains methods to convert a |FilePath| to a |Value| and back.
+// This file contains methods to convert things to a |Value| and back.
 
 #include "base/base_export.h"
 
@@ -14,6 +14,7 @@ class FilePath;
 
 namespace base {
 
+class Time;
 class StringValue;
 class Value;
 
@@ -21,6 +22,9 @@ class Value;
 BASE_EXPORT StringValue* CreateFilePathValue(const FilePath& in_value);
 BASE_EXPORT bool GetValueAsFilePath(const Value& value, FilePath* file_path);
 
+BASE_EXPORT StringValue* CreateTimeValue(const Time& time);
+BASE_EXPORT bool GetValueAsTime(const Value& value, Time* time);
+
 }  // namespace
 
 #endif  // BASE_VALUE_CONVERSIONS_H_
diff --git a/chrome/browser/extensions/api/alarms/alarm_manager.cc b/chrome/browser/extensions/api/alarms/alarm_manager.cc
index 2861a03..1dc8ba5 100644
--- a/chrome/browser/extensions/api/alarms/alarm_manager.cc
+++ b/chrome/browser/extensions/api/alarms/alarm_manager.cc
@@ -8,11 +8,12 @@
 #include "base/json/json_writer.h"
 #include "base/message_loop.h"
 #include "base/time.h"
+#include "base/value_conversions.h"
 #include "base/values.h"
 #include "chrome/browser/extensions/extension_event_router.h"
-#include "chrome/browser/extensions/extension_prefs.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/extension_system.h"
+#include "chrome/browser/extensions/state_store.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "content/public/browser/notification_service.h"
@@ -23,6 +24,10 @@ namespace {
 
 const char kOnAlarmEvent[] = "alarms.onAlarm";
 
+// A list of alarms that this extension has set.
+const char kRegisteredAlarms[] = "alarms";
+const char kAlarmScheduledRunTime[] = "scheduled_run_time";
+
 // The minimum period between polling for alarms to run.
 const base::TimeDelta kDefaultMinPollPeriod = base::TimeDelta::FromMinutes(5);
 
@@ -45,12 +50,52 @@ class DefaultAlarmDelegate : public AlarmManager::Delegate {
   Profile* profile_;
 };
 
+// Contains the state we persist for each alarm.
+struct AlarmState {
+  linked_ptr<AlarmManager::Alarm> alarm;
+  base::Time scheduled_run_time;
+
+  AlarmState() {}
+  ~AlarmState() {}
+};
+
 // 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<AlarmState> AlarmsFromValue(const base::ListValue* list) {
+  typedef AlarmManager::Alarm Alarm;
+  std::vector<AlarmState> alarms;
+  for (size_t i = 0; i < list->GetSize(); ++i) {
+    base::DictionaryValue* alarm_dict = NULL;
+    AlarmState alarm;
+    alarm.alarm.reset(new Alarm());
+    if (list->GetDictionary(i, &alarm_dict) &&
+        Alarm::Populate(*alarm_dict, alarm.alarm.get())) {
+      base::Value* time_value = NULL;
+      if (alarm_dict->Get(kAlarmScheduledRunTime, &time_value))
+        base::GetValueAsTime(*time_value, &alarm.scheduled_run_time);
+      alarms.push_back(alarm);
+    }
+  }
+  return alarms;
+}
+
+scoped_ptr<base::ListValue> AlarmsToValue(
+    const std::vector<AlarmState>& alarms) {
+  scoped_ptr<base::ListValue> list(new ListValue());
+  for (size_t i = 0; i < alarms.size(); ++i) {
+    scoped_ptr<base::DictionaryValue> alarm = alarms[i].alarm->ToValue().Pass();
+    alarm->Set(kAlarmScheduledRunTime,
+               base::CreateTimeValue(alarms[i].scheduled_run_time));
+    list->Append(alarm.release());
+  }
+  return list.Pass();
+}
+
+
 }  // namespace
 
 // AlarmManager
@@ -61,6 +106,10 @@ AlarmManager::AlarmManager(Profile* profile)
       last_poll_time_(base::Time()) {
   registrar_.Add(this, chrome::NOTIFICATION_EXTENSION_LOADED,
                  content::Source<Profile>(profile_));
+
+  StateStore* storage = ExtensionSystem::Get(profile_)->state_store();
+  if (storage)
+    storage->RegisterKey(kRegisteredAlarms);
 }
 
 AlarmManager::~AlarmManager() {
@@ -70,7 +119,7 @@ void AlarmManager::AddAlarm(const std::string& extension_id,
                             const linked_ptr<Alarm>& alarm) {
   base::TimeDelta alarm_time = TimeDeltaFromDelay(alarm->delay_in_minutes);
   AddAlarmImpl(extension_id, alarm, alarm_time);
-  WriteToPrefs(extension_id);
+  WriteToStorage(extension_id);
 }
 
 const AlarmManager::Alarm* AlarmManager::GetAlarm(
@@ -111,7 +160,7 @@ bool AlarmManager::RemoveAlarm(const std::string& extension_id,
     return false;
 
   RemoveAlarmIterator(it);
-  WriteToPrefs(extension_id);
+  WriteToStorage(extension_id);
   return true;
 }
 
@@ -126,7 +175,7 @@ void AlarmManager::RemoveAllAlarms(const std::string& extension_id) {
     RemoveAlarmIterator(AlarmIterator(list, list->second.begin()));
 
   CHECK(alarms_.find(extension_id) == alarms_.end());
-  WriteToPrefs(extension_id);
+  WriteToStorage(extension_id);
 }
 
 void AlarmManager::RemoveAlarmIterator(const AlarmIterator& iter) {
@@ -159,7 +208,7 @@ void AlarmManager::OnAlarm(const std::string& extension_id,
     scheduled_times_[alarm].time =
         last_poll_time_ + TimeDeltaFromDelay(alarm->delay_in_minutes);
   }
-  WriteToPrefs(extension_id_copy);
+  WriteToStorage(extension_id_copy);
 }
 
 void AlarmManager::AddAlarmImpl(const std::string& extension_id,
@@ -180,43 +229,41 @@ void AlarmManager::AddAlarmImpl(const std::string& extension_id,
   ScheduleNextPoll(base::TimeDelta::FromMinutes(0));
 }
 
-void AlarmManager::WriteToPrefs(const std::string& extension_id) {
-  ExtensionService* service =
-      ExtensionSystem::Get(profile_)->extension_service();
-  if (!service || !service->extension_prefs())
+void AlarmManager::WriteToStorage(const std::string& extension_id) {
+  StateStore* storage = ExtensionSystem::Get(profile_)->state_store();
+  if (!storage)
     return;
 
-  std::vector<AlarmPref> alarm_prefs;
-
+  std::vector<AlarmState> alarm_states;
   AlarmMap::iterator list = alarms_.find(extension_id);
   if (list != alarms_.end()) {
     for (AlarmList::iterator it = list->second.begin();
          it != list->second.end(); ++it) {
-      AlarmPref pref;
+      AlarmState pref;
       pref.alarm = *it;
       pref.scheduled_run_time = scheduled_times_[it->get()].time;
-      alarm_prefs.push_back(pref);
+      alarm_states.push_back(pref);
     }
   }
 
-  service->extension_prefs()->SetRegisteredAlarms(extension_id, alarm_prefs);
+  scoped_ptr<Value> alarms(AlarmsToValue(alarm_states).release());
+  storage->SetExtensionValue(extension_id, kRegisteredAlarms, alarms.Pass());
 }
 
-void AlarmManager::ReadFromPrefs(const std::string& extension_id) {
-  ExtensionService* service =
-      ExtensionSystem::Get(profile_)->extension_service();
-  if (!service || !service->extension_prefs())
+void AlarmManager::ReadFromStorage(const std::string& extension_id,
+                                   scoped_ptr<base::Value> value) {
+  base::ListValue* list = NULL;
+  if (!value.get() || !value->GetAsList(&list))
     return;
 
-  std::vector<AlarmPref> alarm_prefs =
-      service->extension_prefs()->GetRegisteredAlarms(extension_id);
-  for (size_t i = 0; i < alarm_prefs.size(); ++i) {
+  std::vector<AlarmState> alarm_states = AlarmsFromValue(list);
+  for (size_t i = 0; i < alarm_states.size(); ++i) {
     base::TimeDelta delay =
-        alarm_prefs[i].scheduled_run_time - base::Time::Now();
+        alarm_states[i].scheduled_run_time - base::Time::Now();
     if (delay < base::TimeDelta::FromSeconds(0))
       delay = base::TimeDelta::FromSeconds(0);
 
-    AddAlarmImpl(extension_id, alarm_prefs[i].alarm, delay);
+    AddAlarmImpl(extension_id, alarm_states[i].alarm, delay);
   }
 }
 
@@ -291,7 +338,12 @@ void AlarmManager::Observe(
     case chrome::NOTIFICATION_EXTENSION_LOADED: {
       const Extension* extension =
           content::Details<const Extension>(details).ptr();
-      ReadFromPrefs(extension->id());
+      StateStore* storage = ExtensionSystem::Get(profile_)->state_store();
+      if (storage) {
+        storage->GetExtensionValue(extension->id(), kRegisteredAlarms,
+            base::Bind(&AlarmManager::ReadFromStorage,
+                       AsWeakPtr(), extension->id()));
+      }
       break;
     }
     default:
@@ -300,10 +352,4 @@ void AlarmManager::Observe(
   }
 }
 
-AlarmPref::AlarmPref() {
-}
-
-AlarmPref::~AlarmPref() {
-}
-
 }  // namespace extensions
diff --git a/chrome/browser/extensions/api/alarms/alarm_manager.h b/chrome/browser/extensions/api/alarms/alarm_manager.h
index 47884f9..6930998 100644
--- a/chrome/browser/extensions/api/alarms/alarm_manager.h
+++ b/chrome/browser/extensions/api/alarms/alarm_manager.h
@@ -10,6 +10,7 @@
 #include <map>
 #include <vector>
 
+#include "base/memory/weak_ptr.h"
 #include "base/timer.h"
 #include "chrome/browser/extensions/extension_function.h"
 #include "chrome/common/extensions/api/alarms.h"
@@ -24,7 +25,9 @@ class ExtensionAlarmsSchedulingTest;
 
 // Manages the currently pending alarms for every extension in a profile.
 // There is one manager per virtual Profile.
-class AlarmManager : public content::NotificationObserver {
+class AlarmManager
+    : public content::NotificationObserver,
+      public base::SupportsWeakPtr<AlarmManager> {
  public:
   typedef extensions::api::alarms::Alarm Alarm;
   typedef std::vector<linked_ptr<Alarm> > AlarmList;
@@ -100,9 +103,10 @@ class AlarmManager : public content::NotificationObserver {
                     const linked_ptr<Alarm>& alarm,
                     base::TimeDelta time_delay);
 
-  // Syncs our alarm data for the given extension to/from the prefs file.
-  void WriteToPrefs(const std::string& extension_id);
-  void ReadFromPrefs(const std::string& extension_id);
+  // 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);
 
   // Schedules the next poll of alarms for when the next soonest alarm runs,
   // but do not more often than min_period.
@@ -135,15 +139,6 @@ class AlarmManager : public content::NotificationObserver {
   base::Time next_poll_time_;
 };
 
-// Contains the data we store in the extension prefs for each alarm.
-struct AlarmPref {
-  linked_ptr<AlarmManager::Alarm> alarm;
-  base::Time scheduled_run_time;
-
-  AlarmPref();
-  ~AlarmPref();
-};
-
 } //  namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_ALARMS_ALARM_MANAGER_H__
diff --git a/chrome/browser/extensions/extension_prefs.cc b/chrome/browser/extensions/extension_prefs.cc
index 6f0f3fb..c0a33f2 100644
--- a/chrome/browser/extensions/extension_prefs.cc
+++ b/chrome/browser/extensions/extension_prefs.cc
@@ -8,7 +8,6 @@
 #include "base/string_util.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/extensions/admin_policy.h"
-#include "chrome/browser/extensions/api/alarms/alarm_manager.h"
 #include "chrome/browser/extensions/api/omnibox/omnibox_api.h"
 #include "chrome/browser/extensions/extension_menu_manager.h"
 #include "chrome/browser/extensions/extension_pref_store.h"
@@ -171,10 +170,6 @@ const char kPrefIncognitoContentSettings[] = "incognito_content_settings";
 // background page.
 const char kRegisteredEvents[] = "events";
 
-// A list of alarms that this extension has set.
-const char kRegisteredAlarms[] = "alarms";
-const char kAlarmScheduledRunTime[] = "scheduled_run_time";
-
 // Persisted value for omnibox.setDefaultSuggestion.
 const char kOmniboxDefaultSuggestion[] = "omnibox_default_suggestion";
 
@@ -957,43 +952,6 @@ void ExtensionPrefs::SetRegisteredEvents(
   UpdateExtensionPref(extension_id, kRegisteredEvents, value);
 }
 
-std::vector<extensions::AlarmPref> ExtensionPrefs::GetRegisteredAlarms(
-    const std::string& extension_id) {
-  std::vector<extensions::AlarmPref> alarms;
-  const base::DictionaryValue* extension = GetExtensionPref(extension_id);
-  if (!extension)
-    return alarms;
-
-  base::ListValue* list = NULL;
-  if (!extension->GetList(kRegisteredAlarms, &list))
-    return alarms;
-
-  typedef extensions::AlarmManager::Alarm Alarm;
-  for (size_t i = 0; i < list->GetSize(); ++i) {
-    base::DictionaryValue* alarm_dict = NULL;
-    extensions::AlarmPref alarm;
-    alarm.alarm.reset(new Alarm());
-    if (list->GetDictionary(i, &alarm_dict) &&
-        Alarm::Populate(*alarm_dict, alarm.alarm.get())) {
-      alarm.scheduled_run_time = ReadTime(alarm_dict, kAlarmScheduledRunTime);
-      alarms.push_back(alarm);
-    }
-  }
-  return alarms;
-}
-
-void ExtensionPrefs::SetRegisteredAlarms(
-    const std::string& extension_id,
-    const std::vector<extensions::AlarmPref>& alarms) {
-  base::ListValue* list = new ListValue();
-  for (size_t i = 0; i < alarms.size(); ++i) {
-    scoped_ptr<base::DictionaryValue> alarm = alarms[i].alarm->ToValue().Pass();
-    SaveTime(alarm.get(), kAlarmScheduledRunTime, alarms[i].scheduled_run_time);
-    list->Append(alarm.release());
-  }
-  UpdateExtensionPref(extension_id, kRegisteredAlarms, list);
-}
-
 extensions::ExtensionOmniboxSuggestion
 ExtensionPrefs::GetOmniboxDefaultSuggestion(const std::string& extension_id) {
   extensions::ExtensionOmniboxSuggestion suggestion;
@@ -1241,7 +1199,6 @@ void ExtensionPrefs::OnExtensionInstalled(
 
   // Clear state that may be registered from a previous install.
   extension_dict->Remove(kRegisteredEvents, NULL);
-  extension_dict->Remove(kRegisteredAlarms, NULL);
   extension_dict->Remove(kPrefContextMenus, NULL);
 
   if (extension->is_app()) {
diff --git a/chrome/browser/extensions/extension_prefs.h b/chrome/browser/extensions/extension_prefs.h
index 37607bf..e6e3cee 100644
--- a/chrome/browser/extensions/extension_prefs.h
+++ b/chrome/browser/extensions/extension_prefs.h
@@ -28,7 +28,6 @@ class PrefService;
 class URLPatternSet;
 
 namespace extensions {
-struct AlarmPref;
 struct ExtensionOmniboxSuggestion;
 }
 
@@ -276,13 +275,6 @@ class ExtensionPrefs : public extensions::ContentSettingsStore::Observer,
   void SetRegisteredEvents(const std::string& extension_id,
                            const std::set<std::string>& events);
 
-  // Controls a list of alarms for this extension, including the next time they
-  // should run.
-  std::vector<extensions::AlarmPref> GetRegisteredAlarms(
-      const std::string& extension_id);
-  void SetRegisteredAlarms(const std::string& extension_id,
-                           const std::vector<extensions::AlarmPref>& alarms);
-
   // Controls the omnibox default suggestion as set by the extension.
   extensions::ExtensionOmniboxSuggestion GetOmniboxDefaultSuggestion(
       const std::string& extension_id);
diff --git a/chrome/browser/extensions/extension_service.cc b/chrome/browser/extensions/extension_service.cc
index 496556f9..62a32a0 100644
--- a/chrome/browser/extensions/extension_service.cc
+++ b/chrome/browser/extensions/extension_service.cc
@@ -189,6 +189,7 @@ const char* ExtensionService::kSyncAppSettingsDirectoryName =
     "Sync App Settings";
 const char* ExtensionService::kSyncExtensionSettingsDirectoryName =
     "Sync Extension Settings";
+const char* ExtensionService::kStateStoreName = "Extension State";
 
 void ExtensionService::CheckExternalUninstall(const std::string& id) {
   CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
diff --git a/chrome/browser/extensions/extension_service.h b/chrome/browser/extensions/extension_service.h
index 911e52a..b79ed33 100644
--- a/chrome/browser/extensions/extension_service.h
+++ b/chrome/browser/extensions/extension_service.h
@@ -171,6 +171,10 @@ class ExtensionService
   // settings are stored.
   static const char* kSyncExtensionSettingsDirectoryName;
 
+  // The name of the database inside the profile where chrome-internal
+  // extension state resides.
+  static const char* kStateStoreName;
+
   // Returns the Extension of hosted or packaged apps, NULL otherwise.
   const extensions::Extension* GetInstalledApp(const GURL& url);
 
diff --git a/chrome/browser/extensions/extension_system.cc b/chrome/browser/extensions/extension_system.cc
index e0e5165..a5793e4 100644
--- a/chrome/browser/extensions/extension_system.cc
+++ b/chrome/browser/extensions/extension_system.cc
@@ -27,6 +27,7 @@
 #include "chrome/browser/extensions/extension_system_factory.h"
 #include "chrome/browser/extensions/lazy_background_task_queue.h"
 #include "chrome/browser/extensions/management_policy.h"
+#include "chrome/browser/extensions/state_store.h"
 #include "chrome/browser/extensions/unpacked_installer.h"
 #include "chrome/browser/extensions/user_script_master.h"
 #include "chrome/browser/prefs/pref_service.h"
@@ -83,6 +84,10 @@ void ExtensionSystemImpl::Shared::InitPrefs() {
       profile_->GetPath().AppendASCII(ExtensionService::kInstallDirectoryName),
       ExtensionPrefValueMapFactory::GetForProfile(profile_)));
   extension_prefs_->Init(extensions_disabled);
+
+  state_store_.reset(new extensions::StateStore(
+      profile_,
+      profile_->GetPath().AppendASCII(ExtensionService::kStateStoreName)));
 }
 
 void ExtensionSystemImpl::Shared::RegisterManagementPolicyProviders() {
@@ -196,6 +201,10 @@ void ExtensionSystemImpl::Shared::Init(bool extensions_enabled) {
   rules_registry_service_->RegisterDefaultRulesRegistries();
 }
 
+extensions::StateStore* ExtensionSystemImpl::Shared::state_store() {
+  return state_store_.get();
+}
+
 ExtensionService* ExtensionSystemImpl::Shared::extension_service() {
   return extension_service_.get();
 }
@@ -298,6 +307,10 @@ extensions::AlarmManager* ExtensionSystemImpl::alarm_manager() {
   return alarm_manager_.get();
 }
 
+extensions::StateStore* ExtensionSystemImpl::state_store() {
+  return shared_->state_store();
+}
+
 ExtensionInfoMap* ExtensionSystemImpl::info_map() {
   return shared_->info_map();
 }
diff --git a/chrome/browser/extensions/extension_system.h b/chrome/browser/extensions/extension_system.h
index 676bdb1..23d228f 100644
--- a/chrome/browser/extensions/extension_system.h
+++ b/chrome/browser/extensions/extension_system.h
@@ -30,6 +30,7 @@ class Extension;
 class LazyBackgroundTaskQueue;
 class ManagementPolicy;
 class RulesRegistryService;
+class StateStore;
 }
 
 // The ExtensionSystem manages the creation and destruction of services
@@ -74,6 +75,9 @@ class ExtensionSystem : public ProfileKeyedService {
   // The AlarmManager is created at startup.
   virtual extensions::AlarmManager* alarm_manager() = 0;
 
+  // The StateStore is created at startup.
+  virtual extensions::StateStore* state_store() = 0;
+
   // Returns the IO-thread-accessible extension data.
   virtual ExtensionInfoMap* info_map() = 0;
 
@@ -126,6 +130,7 @@ class ExtensionSystemImpl : public ExtensionSystem {
   virtual ExtensionDevToolsManager* devtools_manager() OVERRIDE;
   virtual ExtensionProcessManager* process_manager() OVERRIDE;
   virtual extensions::AlarmManager* alarm_manager() OVERRIDE;
+  virtual extensions::StateStore* state_store() OVERRIDE;
   virtual extensions::LazyBackgroundTaskQueue* lazy_background_task_queue()
       OVERRIDE;  // shared
   virtual ExtensionInfoMap* info_map() OVERRIDE;  // shared
@@ -159,6 +164,7 @@ class ExtensionSystemImpl : public ExtensionSystem {
     void InitInfoMap();
     void Init(bool extensions_enabled);
 
+    extensions::StateStore* state_store();
     ExtensionService* extension_service();
     extensions::ManagementPolicy* management_policy();
     UserScriptMaster* user_script_master();
@@ -173,9 +179,9 @@ class ExtensionSystemImpl : public ExtensionSystem {
 
     // The services that are shared between normal and incognito profiles.
 
-    // Keep extension_prefs_ above extension_service_, because the latter
-    // maintains a pointer to the former and must be destructed first.
+    scoped_ptr<extensions::StateStore> state_store_;
     scoped_ptr<ExtensionPrefs> extension_prefs_;
+    // ExtensionService depends on the 2 above.
     scoped_ptr<ExtensionService> extension_service_;
     scoped_ptr<extensions::ManagementPolicy> management_policy_;
     scoped_refptr<UserScriptMaster> user_script_master_;
diff --git a/chrome/browser/extensions/state_store.cc b/chrome/browser/extensions/state_store.cc
new file mode 100644
index 0000000..69d432e
--- /dev/null
+++ b/chrome/browser/extensions/state_store.cc
@@ -0,0 +1,75 @@
+// 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/state_store.h"
+
+#include "chrome/common/chrome_notification_types.h"
+#include "chrome/common/extensions/extension.h"
+#include "content/public/browser/notification_service.h"
+#include "content/public/browser/notification_types.h"
+
+namespace {
+
+std::string GetFullKey(const std::string& extension_id,
+                       const std::string& key) {
+  return extension_id + "." + key;
+}
+
+}  // namespace
+
+namespace extensions {
+
+StateStore::StateStore(Profile* profile, const FilePath& db_path)
+    : store_(db_path) {
+  registrar_.Add(this, chrome::NOTIFICATION_EXTENSION_INSTALLED,
+                 content::Source<Profile>(profile));
+  registrar_.Add(this, chrome::NOTIFICATION_EXTENSION_UNINSTALLED,
+                 content::Source<Profile>(profile));
+}
+
+StateStore::~StateStore() {
+}
+
+void StateStore::RegisterKey(const std::string& key) {
+  registered_keys_.insert(key);
+}
+
+void StateStore::GetExtensionValue(const std::string& extension_id,
+                                   const std::string& key,
+                                   ReadCallback callback) {
+  store_.Get(GetFullKey(extension_id, key), callback);
+}
+
+void StateStore::SetExtensionValue(
+    const std::string& extension_id,
+    const std::string& key,
+    scoped_ptr<base::Value> value) {
+  store_.Set(GetFullKey(extension_id, key), value.Pass());
+}
+
+void StateStore::Observe(int type,
+                         const content::NotificationSource& source,
+                         const content::NotificationDetails& details) {
+  std::string extension_id;
+
+  switch (type) {
+    case chrome::NOTIFICATION_EXTENSION_INSTALLED:
+      extension_id = content::Details<const Extension>(details).ptr()->id();
+      break;
+    case chrome::NOTIFICATION_EXTENSION_UNINSTALLED:
+      extension_id =
+          *content::Details<const std::string>(details).ptr();
+      break;
+    default:
+      NOTREACHED();
+      return;
+  }
+
+  for (std::set<std::string>::iterator key = registered_keys_.begin();
+       key != registered_keys_.end(); ++key) {
+    store_.Remove(GetFullKey(extension_id, *key));
+  }
+}
+
+}  // namespace extensions
diff --git a/chrome/browser/extensions/state_store.h b/chrome/browser/extensions/state_store.h
new file mode 100644
index 0000000..ebaf86b
--- /dev/null
+++ b/chrome/browser/extensions/state_store.h
@@ -0,0 +1,64 @@
+// 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_STATE_STORE_H_
+#define CHROME_BROWSER_EXTENSIONS_STATE_STORE_H_
+#pragma once
+
+#include <set>
+#include <string>
+
+#include "base/memory/weak_ptr.h"
+#include "chrome/browser/value_store/value_store_frontend.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
+
+class Profile;
+
+namespace extensions {
+
+// A storage area for per-extension state that needs to be persisted to disk.
+class StateStore
+    : public base::SupportsWeakPtr<StateStore>,
+      public content::NotificationObserver {
+ public:
+  typedef ValueStoreFrontend::ReadCallback ReadCallback;
+
+  StateStore(Profile* profile, const FilePath& db_path);
+  virtual ~StateStore();
+
+  // Register a key for removal upon extension install/uninstall. We remove
+  // for install to reset state when an extension upgrades.
+  void RegisterKey(const std::string& key);
+
+  // Get the value associated with the given extension and key, and pass
+  // it to |callback| asynchronously.
+  void GetExtensionValue(const std::string& extension_id,
+                         const std::string& key,
+                         ReadCallback callback);
+
+  // Sets a value for a given extension and key.
+  void SetExtensionValue(const std::string& extension_id,
+                         const std::string& key,
+                         scoped_ptr<base::Value> value);
+
+ private:
+  // content::NotificationObserver
+  virtual void Observe(int type,
+                       const content::NotificationSource& source,
+                       const content::NotificationDetails& details) OVERRIDE;
+
+  // The store that holds our key/values.
+  ValueStoreFrontend store_;
+
+  // List of all known keys. They will be cleared for each extension when it is
+  // (un)installed.
+  std::set<std::string> registered_keys_;
+
+  content::NotificationRegistrar registrar_;
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_STATE_STORE_H_
diff --git a/chrome/browser/extensions/test_extension_system.cc b/chrome/browser/extensions/test_extension_system.cc
index 00d69c6..2773d47 100644
--- a/chrome/browser/extensions/test_extension_system.cc
+++ b/chrome/browser/extensions/test_extension_system.cc
@@ -100,6 +100,10 @@ extensions::AlarmManager* TestExtensionSystem::alarm_manager() {
   return alarm_manager_.get();
 }
 
+extensions::StateStore* TestExtensionSystem::state_store() {
+  return NULL;
+}
+
 ExtensionInfoMap* TestExtensionSystem::info_map() {
   return NULL;
 }
diff --git a/chrome/browser/extensions/test_extension_system.h b/chrome/browser/extensions/test_extension_system.h
index 0a29c0c..9461302 100644
--- a/chrome/browser/extensions/test_extension_system.h
+++ b/chrome/browser/extensions/test_extension_system.h
@@ -45,6 +45,7 @@ class TestExtensionSystem : public ExtensionSystem {
   virtual ExtensionDevToolsManager* devtools_manager() OVERRIDE;
   virtual ExtensionProcessManager* process_manager() OVERRIDE;
   virtual extensions::AlarmManager* alarm_manager() OVERRIDE;
+  virtual extensions::StateStore* state_store() OVERRIDE;
   virtual ExtensionInfoMap* info_map() OVERRIDE;
   virtual extensions::LazyBackgroundTaskQueue*
       lazy_background_task_queue() OVERRIDE;
diff --git a/chrome/chrome_browser_extensions.gypi b/chrome/chrome_browser_extensions.gypi
index 9c21acd..a8f0c0e 100644
--- a/chrome/chrome_browser_extensions.gypi
+++ b/chrome/chrome_browser_extensions.gypi
@@ -459,6 +459,8 @@
         'browser/extensions/settings/weak_unlimited_settings_storage.h',
         'browser/extensions/shell_window_registry.cc',
         'browser/extensions/shell_window_registry.h',
+        'browser/extensions/state_store.cc',
+        'browser/extensions/state_store.h',
         'browser/extensions/theme_installed_infobar_delegate.cc',
         'browser/extensions/theme_installed_infobar_delegate.h',
         'browser/extensions/unpacked_installer.cc',