Enable sync for the settings from the Extension Settings API.

chrome/browser/extensions/extension_settings_ui_wrapper.h

+// Copyright (c) 2011 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_EXTENSION_SETTINGS_UI_WRAPPER_H_
+#define CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_UI_WRAPPER_H_
+#pragma once
+
+#include "base/compiler_specific.h"
+#include "base/memory/ref_counted.h"
+#include "base/callback.h"
+#include "chrome/browser/sync/api/syncable_service.h"
+
+class FilePath;
+class ExtensionSettings;
+class ExtensionSettingsStorage;
+
+// Wrapper for an ExtensionSettings object for dealing with thread ownership.
+// This class lives on the UI thread while ExtensionSettings object live on
+// the FILE thread.
+class ExtensionSettingsUIWrapper {
+ public:
+  explicit ExtensionSettingsUIWrapper(const FilePath& base_path);
+
+  typedef base::Callback<void(ExtensionSettings*)> SettingsCallback;
+
+  // Runs |callback| on the FILE thread with the extension settings.
+  void RunWithSettings(const SettingsCallback& callback);
+
+  ~ExtensionSettingsUIWrapper();
+
+ private:
+  // Ref-counted container for the ExtensionSettings object.
+  class Core : public base::RefCountedThreadSafe<Core> {
+   public:
+    // Constructed on UI thread.
+    Core();
+
+    // Does any FILE thread specific initialization, such as
+    // construction of |extension_settings_|.  Must be called before
+    // any call to RunWithSettingsOnFileThread().
+    void InitOnFileThread(const FilePath& base_path);
+
+    // Runs |callback| with extension settings.
+    void RunWithSettingsOnFileThread(const SettingsCallback& callback);
+
+   private:
+    // Can be destroyed on either the UI or FILE thread.
+    virtual ~Core();
+    friend class base::RefCountedThreadSafe<Core>;
+
+    // Lives on the FILE thread.
+    ExtensionSettings* extension_settings_;
+
+    DISALLOW_COPY_AND_ASSIGN(Core);
+  };
+
+  scoped_refptr<Core> core_;
+
+  DISALLOW_COPY_AND_ASSIGN(ExtensionSettingsUIWrapper);
+};
+
+#endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_UI_WRAPPER_H_