Refactored SettingsFrontend and forwarding of calls to the backends.

chrome/browser/extensions/settings/value_store_cache.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_VALUE_STORE_CACHE_H_
+#define CHROME_BROWSER_EXTENSIONS_SETTINGS_VALUE_STORE_CACHE_H_
+
+#include <string>
+
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "base/message_loop_proxy.h"
+
+class ValueStore;
+
+namespace extensions {
+
+class Extension;
+
+// Each namespace of the storage API implements this interface.
+// Instances are created on the UI thread, but from then on live on the loop
+// returned by GetMessageLoop() and every methods (except GetMessageLoop())
+// are always called in that loop, including the destructor.
+class ValueStoreCache {
+ public:
+  typedef base::Callback<void(ValueStore*)> StorageCallback;
+
+  virtual ~ValueStoreCache();
+
+  // Returns the loop that the methods of this class should be invoked on.
+  virtual scoped_refptr<base::MessageLoopProxy> GetMessageLoop() const = 0;
+
+  // Requests the cache to invoke |callback| with the appropriate ValueStore
+  // for the given |extension|. |callback| should be invoked with a NULL
+  // ValueStore in case of errors.
+  virtual void RunWithValueStoreForExtension(
+      const StorageCallback& callback,
+      scoped_refptr<const Extension> extension) = 0;

[not at google - send to devlin, 2012/07/19 06:43:17]

see comment in the other file about making this const Extension*

+
+  // Requests the cache to delete any storage used by |extension_id|.
+  virtual void DeleteStorageSoon(const std::string& extension_id) = 0;
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_SETTINGS_VALUE_STORE_CACHE_H_