[Sync] Removing duplicated includes between cc and h files.

components/sync/api/fake_model_type_service.cc

 // 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.
 
 #include "components/sync/api/fake_model_type_service.h"
 
-#include <string>
-
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
 #include "components/sync/core/data_batch_impl.h"
 #include "components/sync/core/simple_metadata_change_list.h"
 #include "components/sync/syncable/syncable_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 using sync_pb::EntitySpecifics;
 using sync_pb::EntityMetadata;
 using sync_pb::DataTypeState;
@@ skipping 295 matching lines @@
 void FakeModelTypeService::SetConflictResolution(
     ConflictResolution resolution) {
   conflict_resolution_.reset(new ConflictResolution(std::move(resolution)));
 }
 
 void FakeModelTypeService::CheckPostConditions() {
   DCHECK(!service_error_.IsSet());
 }
 
 }  // namespace syncer_v2