Remove duplicated code from sync related unit tests.

sync/api/fake_sync_change_processor.h

 // Copyright 2013 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 SYNC_API_FAKE_SYNC_CHANGE_PROCESSOR_H_
 #define SYNC_API_FAKE_SYNC_CHANGE_PROCESSOR_H_
 
 #include "sync/api/sync_change_processor.h"
 
 namespace syncer {
 
 class FakeSyncChangeProcessor : public SyncChangeProcessor {
  public:
   FakeSyncChangeProcessor();
   virtual ~FakeSyncChangeProcessor();
 
+  // SyncChangeProcessor implementation.
+  //
+  // ProcessSyncChanges will accumulate changes in changes() until they are
+  // cleared.
   virtual syncer::SyncError ProcessSyncChanges(
       const tracked_objects::Location& from_here,
       const syncer::SyncChangeList& change_list) OVERRIDE;
 
+  // SyncChangeProcessor implementation.
+  //
+  // Returns an empty list.
   virtual syncer::SyncDataList GetAllSyncData(syncer::ModelType type)
       const OVERRIDE;
+
+  virtual const syncer::SyncChangeList& changes() const;
+  virtual syncer::SyncChangeList& changes();
+
+ private:
+  syncer::SyncChangeList change_list_;
+
+  DISALLOW_COPY_AND_ASSIGN(FakeSyncChangeProcessor);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_API_FAKE_SYNC_CHANGE_PROCESSOR_H_