[Sync] Implement EstimateMemoryUsage for SharedModelTypeProcessor and ModelTypeWorker

components/sync/base/proto_value_ptr.h

 // Copyright 2015 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_BASE_PROTO_VALUE_PTR_H_
 #define COMPONENTS_SYNC_BASE_PROTO_VALUE_PTR_H_
 
 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
+#include "base/trace_event/memory_usage_estimator.h"
 
 namespace syncer {
 
 class ProcessorEntityTracker;
 struct EntityData;
 
 namespace syncable {
 struct EntryKernel;
 }  // namespace syncable
 
@@ skipping 100 matching lines @@
 
   void load(const void* blob, int length) {
     wrapper_ = Wrapper::ParseFromBlob(blob, length);
   }
 
   scoped_refptr<Wrapper> wrapper_;
 };
 
 template <typename T, typename Traits>
 size_t EstimateMemoryUsage(const ProtoValuePtr<T, Traits>& ptr) {
+  // Including estimators from base::trace_event (memory_usage_estimator.h)
+  // allows to resolve EstimateMemoryUsage name in cases when T is not a sync
+  // protobuf and thus sync_pb::EstimateMemoryUsage doesn't get matched.
+  using base::trace_event::EstimateMemoryUsage;
   return &ptr.value() != &Traits::DefaultValue()
              ? EstimateMemoryUsage(ptr.value())
              : 0;
 }
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_BASE_PROTO_VALUE_PTR_H_