Implement new SyncAPI and convert Preferences to it.

chrome/browser/sync/api/sync_data.h

Index: chrome/browser/sync/api/sync_data.h
diff --git a/chrome/browser/sync/api/sync_data.h b/chrome/browser/sync/api/sync_data.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_SYNC_API_SYNC_DATA_H_
+#define CHROME_BROWSER_SYNC_API_SYNC_DATA_H_
+#pragma once
+
+#include <string>
+#include <vector>
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "chrome/browser/sync/syncable/model_type.h"
+
+namespace sync_pb {
+class EntitySpecifics;
+class SyncEntity;
+}
+
+typedef syncable::ModelType SyncDataType;
+
+// A light-weight container for immutable sync data. Pass-by-value and storage
+// in STL containers are supported and encouraged if helpful.
+class SyncData {
+ public:
+  // Creates an empty and invalid SyncData.
+  SyncData();
+   ~SyncData();
+
+   // Default copy and assign welcome.
+
+  // Helper methods for creating SyncData objects for local data.
+  // Local sync data must always at least set the sync tag.
+  static SyncData CreateLocalData(const std::string& sync_tag);
+  static SyncData CreateLocalData(
+      const std::string& sync_tag,
+      const sync_pb::EntitySpecifics& specifics);
+
+  // Helper method for creating SyncData objects originating from the syncer.
+  static SyncData CreateRemoteData(
+      const sync_pb::SyncEntity& entity);
+  static SyncData CreateRemoteData(
+    const sync_pb::EntitySpecifics& specifics);
+
+  // Whether this SyncData holds valid data. The only way to have a SyncData
+  // without valid data is to use the default constructor.
+  bool IsValid() const;
+  // Return the datatype we're holding information about. Derived from the sync
+  // datatype specifics.
+  SyncDataType GetDataType() const;
+  // Return the current sync datatype specifics.
+  const sync_pb::EntitySpecifics& GetSpecifics() const;
+  // Returns the value of the unique client tag. This is only set for data going
+  // TO the syncer, not coming from.
+  const std::string& GetTag() const;
+  // Whether this sync data is for local data or data coming from the syncer.
+  bool IsLocal() const;
+
+  // TODO(zea): Query methods for other sync properties: title, parent,
+  // successor, etc. Possibly support for hashed tag and sync id?
+
+ private:
+  // A reference counted immutable SyncEntity.
+  class SharedSyncEntity : public
+      base::RefCountedThreadSafe<SharedSyncEntity> {
+   public:
+    // Takes ownership of |sync_entity|'s contents.
+    explicit SharedSyncEntity(sync_pb::SyncEntity* sync_entity);
+
+    // Returns immutable reference to local sync entity.
+    const sync_pb::SyncEntity& sync_entity() const;
+
+   private:
+    friend class base::RefCountedThreadSafe<SharedSyncEntity>;
+
+    // Private due to ref counting.
+    ~SharedSyncEntity();
+
+    scoped_ptr<sync_pb::SyncEntity> sync_entity_;
+  };
+
+  // The actual shared sync entity being held.
+  scoped_refptr<SharedSyncEntity> shared_entity_;
+
+  // Whether this data originated locally or from the syncer (remote data).
+  bool is_local_;
+};
+
+#endif  // CHROME_BROWSER_SYNC_API_SYNC_DATA_H_