Enable sync for the settings from the Extension Settings API.

chrome/browser/extensions/syncable_extension_settings_storage.h

Index: chrome/browser/extensions/syncable_extension_settings_storage.h
diff --git a/chrome/browser/extensions/syncable_extension_settings_storage.h b/chrome/browser/extensions/syncable_extension_settings_storage.h
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+// 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_SYNCABLE_EXTENSION_SETTINGS_STORAGE_H_
+#define CHROME_BROWSER_EXTENSIONS_SYNCABLE_EXTENSION_SETTINGS_STORAGE_H_
+#pragma once
+
+#include "base/compiler_specific.h"
+#include "base/memory/weak_ptr.h"
+#include "base/values.h"
+#include "chrome/browser/extensions/extension_settings_storage.h"
+#include "chrome/browser/extensions/extension_setting_sync_data.h"
+#include "chrome/browser/sync/api/syncable_service.h"
+#include "chrome/browser/sync/api/sync_change.h"
+
+// Decorates an ExtensionSettingsStorage with sync behaviour.
+class SyncableExtensionSettingsStorage : public ExtensionSettingsStorage {
+ public:
+  explicit SyncableExtensionSettingsStorage(
+      std::string extension_id,
+      // Ownership taken.
+      ExtensionSettingsStorage* delegate);
+
+  virtual ~SyncableExtensionSettingsStorage();
+
+  // ExtensionSettingsStorage implementation.
+  virtual Result Get(const std::string& key) OVERRIDE;
+  virtual Result Get(const std::vector<std::string>& keys) OVERRIDE;
+  virtual Result Get() OVERRIDE;
+  virtual Result Set(const std::string& key, const Value& value) OVERRIDE;
+  virtual Result Set(const DictionaryValue& settings) OVERRIDE;
+  virtual Result Remove(const std::string& key) OVERRIDE;
+  virtual Result Remove(const std::vector<std::string>& keys) OVERRIDE;
+  virtual Result Clear() OVERRIDE;
+
+  // Sync-related methods.
+  void StartSyncing(
+      const DictionaryValue& sync_state,
+      // Must be non-NULL. Ownership NOT taken.
+      SyncChangeProcessor* sync_processor);
+  void StopSyncing();
+  void ProcessSyncChanges(const ExtensionSettingSyncDataList& sync_changes);
+
+ private:
+  // Either adds to sync or send updates to sync for some settings.
+  // Whether they're adds or updates depends on the state of synced_keys_.
+  void SendAddsOrUpdatesToSync(const DictionaryValue& settings);
+
+  // Sends deletes to sync for some settings.
+  void SendDeletesToSync(const std::vector<std::string>& keys);
+
+  // Sends all local settings to sync (synced settings assumed to be empty).
+  void SendLocalSettingsToSync(
+      const DictionaryValue& settings);
+
+  // Overwrites local state with sync state.
+  void OverwriteLocalSettingsWithSync(
+      const DictionaryValue& sync_state, const DictionaryValue& settings);
+
+  // Id of the extension these settings are for.
+  std::string extension_id_;
+
+  // Storage area to sync.
+  scoped_ptr<ExtensionSettingsStorage> delegate_;
+
+  // Sync processor.  Non-NULL while sync is enabled (between calls to
+  // StartSyncing and StopSyncing).
+  SyncChangeProcessor* sync_processor_;
+
+  // Keys of the settings that are currently being synced.
+  std::set<std::string> synced_keys_;
+
+  DISALLOW_COPY_AND_ASSIGN(SyncableExtensionSettingsStorage);
+};
+
+#endif  // CHROME_BROWSER_EXTENSIONS_SYNCABLE_EXTENSION_SETTINGS_STORAGE_H_