[Sync] Implement EstimateMemoryUsage for SharedModelTypeProcessor and ModelTypeWorker

components/sync/engine/non_blocking_sync_common.h

 // 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_ENGINE_NON_BLOCKING_SYNC_COMMON_H_
 #define COMPONENTS_SYNC_ENGINE_NON_BLOCKING_SYNC_COMMON_H_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 42 matching lines @@
   EntityDataPtr entity;
 
   int64_t response_version = 0;
   std::string encryption_key_name;
 };
 
 using CommitRequestDataList = std::vector<CommitRequestData>;
 using CommitResponseDataList = std::vector<CommitResponseData>;
 using UpdateResponseDataList = std::vector<UpdateResponseData>;
 
+// Returns the estimate of dynamically allocated memory in bytes.
+size_t EstimateMemoryUsage(const CommitRequestData& value);
+size_t EstimateMemoryUsage(const UpdateResponseData& value);
+
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_ENGINE_NON_BLOCKING_SYNC_COMMON_H_