[Sync] Implement EstimateMemoryUsage for SharedModelTypeProcessor and ModelTypeWorker

components/sync/engine_impl/model_type_worker.cc

Index: components/sync/engine_impl/model_type_worker.cc
diff --git a/components/sync/engine_impl/model_type_worker.cc b/components/sync/engine_impl/model_type_worker.cc
index e7f364d1b9433224b5b97b91cd316db06f8f3748..3f0856f9a03bafe38786551eb60e009d417b13f1 100644
--- a/components/sync/engine_impl/model_type_worker.cc
+++ b/components/sync/engine_impl/model_type_worker.cc
@@ -16,11 +16,13 @@
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/stringprintf.h"
+#include "base/trace_event/memory_usage_estimator.h"
 #include "components/sync/base/time.h"
 #include "components/sync/engine/model_type_processor.h"
 #include "components/sync/engine_impl/commit_contribution.h"
 #include "components/sync/engine_impl/non_blocking_type_commit_contribution.h"
 #include "components/sync/engine_impl/worker_entity_tracker.h"
+#include "components/sync/protocol/proto_memory_estimations.h"
 #include "components/sync/syncable/syncable_util.h"
 
 namespace syncer {
@@ -330,6 +332,15 @@ void ModelTypeWorker::AbortMigration() {
   nudge_handler_->NudgeForInitialDownload(type_);
 }
 
+size_t ModelTypeWorker::EstimateMemoryUsage() const {
+  using base::trace_event::EstimateMemoryUsage;
+  size_t memory_usage = 0;

[Patrick Noland, 2017/03/29 19:42:54]

Should cryptographer be included, since the worker has a private copy?

[pavely, 2017/03/30 01:07:25]

I Included fields that can grow arbitrarily large with number of entities. I
could add cryptographer, it would show fixed cost per datatype and would pollute
cryptographer's class with memory estimation code.

+  memory_usage += EstimateMemoryUsage(model_type_state_);
+  memory_usage += EstimateMemoryUsage(entities_);
+  memory_usage += EstimateMemoryUsage(pending_updates_);
+  return memory_usage;
+}
+
 base::WeakPtr<ModelTypeWorker> ModelTypeWorker::AsWeakPtr() {
   return weak_ptr_factory_.GetWeakPtr();
 }