[Sync] Adding a passthrough MetadataChangeList implementation.

components/sync/model/simple_metadata_change_list_unittest.cc

 // Copyright 2016 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.
 
 #include "components/sync/model/simple_metadata_change_list.h"
 
 #include <set>
 
 #include "base/bind.h"
 #include "base/run_loop.h"
@@ skipping 50 matching lines @@
   std::string global_metadata;
   store()->RegisterWriteMetadataHandler(
       base::Bind(&RecordMetadataWrite, &change_map));
   store()->RegisterWriteGlobalMetadataHandler(
       base::Bind(&RecordGlobalMetadataWrite, &global_metadata));
   store()->RegisterDeleteMetadataHandler(
       base::Bind(&RecordMetadataDelete, &delete_set));
 
   cl.TransferChanges(store(), batch.get());
 
-  EXPECT_EQ(change_map.size(), 0ul);
-  EXPECT_EQ(delete_set.size(), 0ul);
-  EXPECT_EQ(global_metadata.size(), 0ul);
+  EXPECT_EQ(change_map.size(), 0u);
+  EXPECT_EQ(delete_set.size(), 0u);
+  EXPECT_EQ(global_metadata.size(), 0u);
 }
 
 TEST_F(SimpleMetadataChangeListTest, TransferChangesClearsLocalState) {
   SimpleMetadataChangeList cl;
   sync_pb::EntityMetadata metadata;
   metadata.set_client_tag_hash("some_hash");
   cl.UpdateMetadata("client_tag", metadata);
 
   sync_pb::ModelTypeState state;
   state.set_encryption_key_name("ekn");
   cl.UpdateModelTypeState(state);
 
-  EXPECT_NE(cl.GetMetadataChanges().size(), 0ul);
+  EXPECT_NE(cl.GetMetadataChanges().size(), 0u);
   EXPECT_TRUE(cl.HasModelTypeStateChange());
 
   std::unique_ptr<WriteBatch> batch = store()->CreateWriteBatch();
   cl.TransferChanges(store(), batch.get());
 
-  EXPECT_EQ(cl.GetMetadataChanges().size(), 0ul);
+  EXPECT_EQ(cl.GetMetadataChanges().size(), 0u);
   EXPECT_FALSE(cl.HasModelTypeStateChange());
 }
 
 TEST_F(SimpleMetadataChangeListTest, TransferChangesMultipleInvocationsSafe) {
   SimpleMetadataChangeList cl;
   sync_pb::EntityMetadata metadata;
   metadata.set_client_tag_hash("some_hash");
   cl.UpdateMetadata("client_tag", metadata);
 
   sync_pb::ModelTypeState state;
@@ skipping 79 matching lines @@
   cl.TransferChanges(store(), batch.get());
 
   EXPECT_TRUE(delete_set.find("client_tag") != delete_set.end());
   EXPECT_TRUE(change_map.find("client_tag") == change_map.end());
   EXPECT_TRUE(delete_called);
   EXPECT_TRUE(global_metadata.empty());
 }
 
 }  // namespace
 }  // namespace syncer