[Sync] Rework SharedValue<T> into Immutable<T>

chrome/browser/sync/api/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_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"
+#include "chrome/browser/sync/util/immutable.h"
 
 namespace sync_pb {
 class EntitySpecifics;
 class SyncEntity;
-}
+}  // namespace sync_pb
 
 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();
@@ skipping 40 matching lines @@
   // Returns the non unique title (for debugging). Currently only set for data
   // going TO the syncer, not from.
   const std::string& GetTitle() 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: parent, successor, etc.
 
  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);
+  // Necessary since we forward-declare sync_pb::SyncEntity; see
+  // comments in immutable.h.
+  struct ImmutableSyncEntityTraits {
+    typedef sync_pb::SyncEntity* Wrapper;
 
-    // Returns immutable reference to local sync entity.
-    const sync_pb::SyncEntity& sync_entity() const;
+    static void InitializeWrapper(Wrapper* wrapper);
 
-   private:
-    friend class base::RefCountedThreadSafe<SharedSyncEntity>;
+    static void DestroyWrapper(Wrapper* wrapper);
 
-    // Private due to ref counting.
-    ~SharedSyncEntity();
+    static const sync_pb::SyncEntity& Unwrap(const Wrapper& wrapper);
 
-    scoped_ptr<sync_pb::SyncEntity> sync_entity_;
+    static sync_pb::SyncEntity* UnwrapMutable(Wrapper* wrapper);
+
+    static void Swap(sync_pb::SyncEntity* t1, sync_pb::SyncEntity* t2);
   };
 
-  // The actual shared sync entity being held.
-  scoped_refptr<SharedSyncEntity> shared_entity_;
+  typedef browser_sync::Immutable<
+    sync_pb::SyncEntity, ImmutableSyncEntityTraits>
+      ImmutableSyncEntity;
+
+  // Clears |entity|.
+  SyncData(sync_pb::SyncEntity* entity, bool is_local);
+
+  // Whether this SyncData holds valid data.
+  bool is_valid_;
 
   // Whether this data originated locally or from the syncer (remote data).
   bool is_local_;
+
+  // The actual shared sync entity being held.
+  ImmutableSyncEntity immutable_entity_;
 };
 
 #endif  // CHROME_BROWSER_SYNC_API_SYNC_DATA_H_