Implement new SyncAPI and convert Preferences to it.

chrome/browser/sync/api/sync_change_processor.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_SYNC_API_SYNC_CHANGE_PROCESSOR_H_
+#define CHROME_BROWSER_SYNC_API_SYNC_CHANGE_PROCESSOR_H_
+#pragma once
+
+#include <vector>
+
+class SyncChange;
+
+typedef std::vector<SyncChange> SyncChangeList;
+
+// An interface for services that handle receiving SyncChanges.
+class SyncChangeProcessor {
+ public:
+  // Process a list of SyncChanges.
+  virtual void ProcessSyncChanges(const SyncChangeList& change_list) = 0;
+ protected:
+  virtual ~SyncChangeProcessor();
+};
+
+
+#endif  // CHROME_BROWSER_SYNC_API_SYNC_CHANGE_PROCESSOR_H_