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

chrome/browser/extensions/api/storage/local_storage_backend.cc

Index: chrome/browser/extensions/api/storage/local_storage_backend.cc
diff --git a/chrome/browser/extensions/api/storage/local_storage_backend.cc b/chrome/browser/extensions/api/storage/local_storage_backend.cc
new file mode 100644
index 0000000000000000000000000000000000000000..7e4880aca0a3a0e5bbd92bdd9b82728bd6142d5b
--- /dev/null
+++ b/chrome/browser/extensions/api/storage/local_storage_backend.cc
@@ -0,0 +1,37 @@
+// Copyright 2014 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/local_storage_backend.h"
+
+#include "base/file_util.h"
+#include "chrome/browser/extensions/api/storage/settings_storage_factory.h"
+
+namespace extensions {
+
+LocalStorageBackend::LocalStorageBackend(
+    const scoped_refptr<SettingsStorageFactory>& storage_factory,
+    const base::FilePath& base_path,
+    const SettingsStorageQuotaEnforcer::Limits& quota)
+    : SettingsBackend(storage_factory, base_path, quota) {}
+
+LocalStorageBackend::~LocalStorageBackend() {}
+
+ValueStore* LocalStorageBackend::GetStorage(const std::string& extension_id) {
+  StorageMap::iterator iter = storage_map_.find(extension_id);
+  if (iter != storage_map_.end())
+    return iter->second.get();
+
+  linked_ptr<SettingsStorageQuotaEnforcer> storage(
+      CreateStorageForExtension(extension_id).release());
+  storage_map_[extension_id] = storage;
+  return storage.get();
+}
+
+void LocalStorageBackend::DeleteStorage(const std::string& extension_id) {
+  // Clear settings when the extension is uninstalled.
+  storage_map_.erase(extension_id);
+  storage_factory()->DeleteDatabaseIfExists(base_path(), extension_id);
+}
+
+}  // namespace extensions