Resubmit: Add a Restore() method to ValueStore and make StorageAPI use it

chrome/browser/extensions/api/storage/sync_or_local_value_store_cache.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/storage/sync_or_local_value_store_cache.h"
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/sequenced_task_runner.h"
-#include "chrome/browser/extensions/api/storage/settings_backend.h"
+#include "chrome/browser/extensions/api/storage/local_storage_backend.h"
 #include "chrome/browser/extensions/api/storage/settings_frontend.h"
 #include "chrome/browser/extensions/api/storage/settings_storage_quota_enforcer.h"
+#include "chrome/browser/extensions/api/storage/sync_storage_backend.h"
 #include "chrome/browser/extensions/api/storage/weak_unlimited_settings_storage.h"
 #include "chrome/browser/sync/glue/sync_start_util.h"
 #include "content/public/browser/browser_thread.h"
 #include "extensions/common/constants.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/permissions/api_permission.h"
 
 using content::BrowserThread;
 
 namespace extensions {
 
 SyncOrLocalValueStoreCache::SyncOrLocalValueStoreCache(
     settings_namespace::Namespace settings_namespace,
     const scoped_refptr<SettingsStorageFactory>& factory,
     const SettingsStorageQuotaEnforcer::Limits& quota,
     const scoped_refptr<SettingsObserverList>& observers,
     const base::FilePath& profile_path)
-    : settings_namespace_(settings_namespace) {
+    : settings_namespace_(settings_namespace), initialized_(false) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   DCHECK(settings_namespace_ == settings_namespace::LOCAL ||
          settings_namespace_ == settings_namespace::SYNC);
 
   // This post is safe since the destructor can only be invoked from the
   // same message loop, and any potential post of a deletion task must come
   // after the constructor returns.
   BrowserThread::PostTask(
       BrowserThread::FILE, FROM_HERE,
       base::Bind(&SyncOrLocalValueStoreCache::InitOnFileThread,
                  base::Unretained(this),
                  factory, quota, observers, profile_path));
 }
 
 SyncOrLocalValueStoreCache::~SyncOrLocalValueStoreCache() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
 }
 
-SettingsBackend* SyncOrLocalValueStoreCache::GetAppBackend() const {
+syncer::SyncableService* SyncOrLocalValueStoreCache::GetSyncableService(
+    syncer::ModelType type) const {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
-  DCHECK(app_backend_.get());
-  return app_backend_.get();
-}
-
-SettingsBackend* SyncOrLocalValueStoreCache::GetExtensionBackend() const {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
-  DCHECK(extension_backend_.get());
-  return extension_backend_.get();
+  DCHECK(initialized_);
+  switch (type) {
+    case syncer::APP_SETTINGS:
+      return app_backend_->GetAsSyncableService();
+    case syncer::EXTENSION_SETTINGS:
+      return extension_backend_->GetAsSyncableService();
+    default:
+      NOTREACHED();
+      return NULL;
+  }
 }
 
 void SyncOrLocalValueStoreCache::RunWithValueStoreForExtension(
     const StorageCallback& callback,
     scoped_refptr<const Extension> extension) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
-  DCHECK(app_backend_.get());
-  DCHECK(extension_backend_.get());
+  DCHECK(initialized_);
+
   SettingsBackend* backend =
       extension->is_app() ? app_backend_.get() : extension_backend_.get();
   ValueStore* storage = backend->GetStorage(extension->id());
 
   // A neat way to implement unlimited storage; if the extension has the
   // unlimited storage permission, force through all calls to Set() (in the
   // same way that writes from sync ignore quota).
   // But only if it's local storage (bad stuff would happen if sync'ed
   // storage is allowed to be unlimited).
   bool is_unlimited =
       settings_namespace_ == settings_namespace::LOCAL &&
       extension->HasAPIPermission(APIPermission::kUnlimitedStorage);
 
   if (is_unlimited) {
     WeakUnlimitedSettingsStorage unlimited_storage(storage);
     callback.Run(&unlimited_storage);
   } else {
     callback.Run(storage);
   }
 }
 
 void SyncOrLocalValueStoreCache::DeleteStorageSoon(
     const std::string& extension_id) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  DCHECK(initialized_);
   app_backend_->DeleteStorage(extension_id);
   extension_backend_->DeleteStorage(extension_id);
 }
 
 void SyncOrLocalValueStoreCache::InitOnFileThread(
     const scoped_refptr<SettingsStorageFactory>& factory,
     const SettingsStorageQuotaEnforcer::Limits& quota,
     const scoped_refptr<SettingsObserverList>& observers,
     const base::FilePath& profile_path) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
-  DCHECK(!app_backend_.get());
-  DCHECK(!extension_backend_.get());
-  const bool local = settings_namespace_ == settings_namespace::LOCAL;
-  const base::FilePath app_path = profile_path.AppendASCII(
-      local ? extensions::kLocalAppSettingsDirectoryName
-            : extensions::kSyncAppSettingsDirectoryName);
-  const base::FilePath extension_path = profile_path.AppendASCII(
-      local ? extensions::kLocalExtensionSettingsDirectoryName
-            : extensions::kSyncExtensionSettingsDirectoryName);
-  app_backend_.reset(new SettingsBackend(
-      factory, app_path, syncer::APP_SETTINGS,
-      sync_start_util::GetFlareForSyncableService(profile_path),
-      quota, observers));
-  extension_backend_.reset(new SettingsBackend(
-      factory, extension_path, syncer::EXTENSION_SETTINGS,
-      sync_start_util::GetFlareForSyncableService(profile_path),
-      quota, observers));
+  DCHECK(!initialized_);
+  switch (settings_namespace_) {
+    case settings_namespace::LOCAL:
+      app_backend_.reset(new LocalStorageBackend(
+          factory,
+          profile_path.AppendASCII(kLocalAppSettingsDirectoryName),
+          quota));
+      extension_backend_.reset(new LocalStorageBackend(
+          factory,
+          profile_path.AppendASCII(kLocalExtensionSettingsDirectoryName),
+          quota));
+      break;
+    case settings_namespace::SYNC:
+      app_backend_.reset(new SyncStorageBackend(
+          factory,
+          profile_path.AppendASCII(kSyncAppSettingsDirectoryName),
+          quota,
+          observers,
+          syncer::APP_SETTINGS,
+          sync_start_util::GetFlareForSyncableService(profile_path)));
+      extension_backend_.reset(new SyncStorageBackend(
+          factory,
+          profile_path.AppendASCII(kSyncExtensionSettingsDirectoryName),
+          quota,
+          observers,
+          syncer::EXTENSION_SETTINGS,
+          sync_start_util::GetFlareForSyncableService(profile_path)));
+      break;
+    default:
+      NOTREACHED();
+  }
+
+  initialized_ = true;
 }
 
 }  // namespace extensions