Revert of [sync] Replace FakeServer's implementation with LoopbackServer invocations.

components/sync/test/fake_server/unique_client_entity.h

Index: components/sync/test/fake_server/unique_client_entity.h
diff --git a/components/sync/test/fake_server/unique_client_entity.h b/components/sync/test/fake_server/unique_client_entity.h
new file mode 100644
index 0000000000000000000000000000000000000000..5fe819dcd48ebf7c5cde6d88b33b31ce22ec83d5
--- /dev/null
+++ b/components/sync/test/fake_server/unique_client_entity.h
@@ -0,0 +1,68 @@
+// Copyright 2014 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 COMPONENTS_SYNC_TEST_FAKE_SERVER_UNIQUE_CLIENT_ENTITY_H_
+#define COMPONENTS_SYNC_TEST_FAKE_SERVER_UNIQUE_CLIENT_ENTITY_H_
+
+#include <stdint.h>
+
+#include <memory>
+#include <string>
+
+#include "components/sync/base/model_type.h"
+#include "components/sync/test/fake_server/fake_server_entity.h"
+
+namespace sync_pb {
+class EntitySpecifics;
+class SyncEntity;
+}  // namespace sync_pb
+
+namespace fake_server {
+
+// An entity that is unique per client account.
+//
+// TODO(pvalenzuela): Reconsider the naming of this class. In some cases, this
+// type is used to represent entities where the unique client tag is irrelevant
+// (e.g., Autofill Wallet).
+class UniqueClientEntity : public FakeServerEntity {
+ public:
+  UniqueClientEntity(const std::string& id,
+                     const std::string& client_defined_unique_tag,
+                     syncer::ModelType model_type,
+                     int64_t version,
+                     const std::string& name,
+                     const sync_pb::EntitySpecifics& specifics,
+                     int64_t creation_time,
+                     int64_t last_modified_time);
+
+  ~UniqueClientEntity() override;
+
+  // Factory function for creating a UniqueClientEntity.
+  static std::unique_ptr<FakeServerEntity> Create(
+      const sync_pb::SyncEntity& client_entity);
+
+  // Factory function for creating a UniqueClientEntity for use in the
+  // FakeServer injection API.
+  static std::unique_ptr<FakeServerEntity> CreateForInjection(
+      const std::string& name,
+      const sync_pb::EntitySpecifics& entity_specifics);
+
+  // Derives an ID from a unique client tagged entity.
+  static std::string EffectiveIdForClientTaggedEntity(
+      const sync_pb::SyncEntity& entity);
+
+  // FakeServerEntity implementation.
+  bool RequiresParentId() const override;
+  std::string GetParentId() const override;
+  void SerializeAsProto(sync_pb::SyncEntity* proto) const override;
+
+ private:
+  // These member values have equivalent fields in SyncEntity.
+  int64_t creation_time_;
+  int64_t last_modified_time_;
+};
+
+}  // namespace fake_server
+
+#endif  // COMPONENTS_SYNC_TEST_FAKE_SERVER_UNIQUE_CLIENT_ENTITY_H_