WORK IN PROGRESS.

chrome/browser/extensions/extension_settings_sync_data.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_SYNC_DATA_H_
+#define CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_SYNC_DATA_H_
+#pragma once
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/values.h"
+#include "chrome/browser/sync/api/sync_data.h"
+#include "chrome/browser/sync/api/sync_change.h"
+
+// Container for data interpreted from sync data/changes.  Safe and efficient
+// to copy.
+// XXX rename this to ExtensionSettingSyncData (*not plural*)
+class ExtensionSettingsSyncData {
+ public:
+  // Creates from a sync change.
+  explicit ExtensionSettingsSyncData(const SyncChange& sync_change);
+
+  // Creates from sync data.  change_type will be ACTION_INVALID.
+  explicit ExtensionSettingsSyncData(const SyncData& sync_data);
+
+  // Construct manually.
+  explicit ExtensionSettingsSyncData(
+      SyncChange::SyncChangeType change_type,
+      const std::string& extension_id,
+      const std::string& key,
+      // May be NULL.  Ownership taken if not.
+      Value* value);
+
+  // Returns the type of the sync change; may be INVALID if this is not
+  // constructed from a SyncChange.
+  SyncChange::SyncChangeType change_type() const;
+
+  // Returns the extension id the setting is for.
+  const std::string& extension_id() const;
+
+  // Returns the settings key.
+  const std::string& key() const;
+
+  // Returns the value of the setting, possibly NULL.
+  // Ownership NOT given up.
+  const Value* value() const;
+
+  // Returns a string representation of the data.
+  std::string ToString() const;
+
+ private:
+  // Ref-counted container for the data.
+  class Internal : public base::RefCountedThreadSafe<Internal> {
+   public:
+    explicit Internal(
+      SyncChange::SyncChangeType change_type,
+      const std::string& extension_id,
+      const std::string& key,
+      Value* value);
+
+    SyncChange::SyncChangeType change_type_;
+    std::string extension_id_;
+    std::string key_;
+    scoped_ptr<Value> value_;
+
+   private:
+    friend class base::RefCountedThreadSafe<Internal>;
+    ~Internal();
+    DISALLOW_COPY_AND_ASSIGN(Internal);
+  };
+
+  scoped_refptr<Internal> internal_;
+};
+
+typedef std::vector<ExtensionSettingsSyncData> ExtensionSettingsSyncDataList;
+
+#endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SETTINGS_SYNC_DATA_H_