Refactored SettingsFrontend and forwarding of calls to the backends.

chrome/browser/extensions/settings/settings_frontend.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_SETTINGS_SETTINGS_FRONTEND_H_
 #define CHROME_BROWSER_EXTENSIONS_SETTINGS_SETTINGS_FRONTEND_H_
 
+#include <map>
 #include <string>
 
 #include "base/callback.h"
-#include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list_threadsafe.h"
 #include "chrome/browser/extensions/settings/settings_namespace.h"
 #include "chrome/browser/extensions/settings/settings_observer.h"
 #include "chrome/browser/extensions/settings/settings_storage_factory.h"
 #include "chrome/browser/extensions/settings/settings_storage_quota_enforcer.h"
-#include "chrome/browser/value_store/leveldb_value_store.h"
+#include "chrome/browser/extensions/settings/value_store_cache.h"
 #include "sync/api/syncable_service.h"
 
 class Profile;
 class ValueStore;
 
 namespace extensions {
 
 // The component of extension settings which runs on the UI thread, as opposed
 // to SettingsBackend which lives on the FILE thread.
 // All public methods, must be called on the UI thread, with the exception of
 // GetBackendForSync(), which must be called on the FILE thread.
 class SettingsFrontend {
  public:
-  // Creates with the default factory. Ownership of |profile| not taken.
+  // Creates with the default factory.
   static SettingsFrontend* Create(Profile* profile);
 
   // Creates with a specific factory |storage_factory| (presumably for tests).
-  // Ownership of |profile| not taken.
   static SettingsFrontend* Create(
       const scoped_refptr<SettingsStorageFactory>& storage_factory,
-      // Owership NOT taken.
       Profile* profile);
 
   virtual ~SettingsFrontend();
 
-  typedef base::Callback<void(syncer::SyncableService*)>
-      SyncableServiceCallback;
-  typedef base::Callback<void(ValueStore*)> StorageCallback;
-
   // Must only be called from the FILE thread. |type| should be either
   // APP_SETTINGS or EXTENSION_SETTINGS.
   syncer::SyncableService* GetBackendForSync(syncer::ModelType type) const;
 
-  // Runs |callback| on the FILE thread with the storage area for
-  // |extension_id|.  If there is no extension with that ID, the storage area
-  // will be NULL.
+  // Runs |callback| with the storage area of the given |settings_namespace|
+  // for the |extension_id|. If there is no extension with that ID, the storage
+  // area will be NULL.
   void RunWithStorage(
       const std::string& extension_id,
       settings_namespace::Namespace settings_namespace,
-      const StorageCallback& callback);
+      const ValueStoreCache::StorageCallback& callback);
 
-  // Deletes the settings for an extension (on the FILE thread).
+  // Deletes the settings for the given |extension_id|.
   void DeleteStorageSoon(const std::string& extension_id);
 
   // Gets the thread-safe observer list.
   scoped_refptr<SettingsObserverList> GetObservers();
 
  private:
+  typedef std::map<settings_namespace::Namespace, ValueStoreCache*> CacheMap;
+
   SettingsFrontend(
       const scoped_refptr<SettingsStorageFactory>& storage_factory,
-      // Ownership NOT taken.
       Profile* profile);
 
   // The quota limit configurations for the local and sync areas, taken out of
   // the schema in chrome/common/extensions/api/storage.json.
   const SettingsStorageQuotaEnforcer::Limits local_quota_limit_;
   const SettingsStorageQuotaEnforcer::Limits sync_quota_limit_;
 
   // The (non-incognito) Profile this Frontend belongs to.
   Profile* const profile_;
 
   // List of observers to settings changes.
   scoped_refptr<SettingsObserverList> observers_;
 
   // Observer for |profile_|.
   scoped_ptr<SettingsObserver> profile_observer_;
 
-  // Ref-counted container for each SettingsBackend object.  There are 4: an
-  // apps and an extensions Backend for the LOCAL namespace, and likewise for
-  // the SYNC namespace.  They only differ in what directory the database for
-  // each exists in.
-  class BackendWrapper;
-  struct BackendWrappers {
-    BackendWrappers();
-    ~BackendWrappers();
-    scoped_refptr<BackendWrapper> app;
-    scoped_refptr<BackendWrapper> extension;
-  };
-  std::map<settings_namespace::Namespace, BackendWrappers> backends_;
+  // Maps a known namespace to its corresponding ValueStoreCache. The caches
+  // are owned by this object.
+  CacheMap caches_;
 
   DISALLOW_COPY_AND_ASSIGN(SettingsFrontend);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_SETTINGS_SETTINGS_FRONTEND_H_