Convert //sync from scoped_ptr to std::unique_ptr

sync/engine/directory_commit_contributor.cc

 // 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.
 
 #include "sync/engine/directory_commit_contributor.h"
 
 #include <stddef.h>
 
 #include "sync/engine/directory_commit_contribution.h"
 #include "sync/sessions/directory_type_debug_info_emitter.h"
 
 namespace syncer {
 
 DirectoryCommitContributor::DirectoryCommitContributor(
     syncable::Directory* dir,
     ModelType type,
     DirectoryTypeDebugInfoEmitter* debug_info_emitter)
     : dir_(dir),
       type_(type),
       debug_info_emitter_(debug_info_emitter) {}
 
 DirectoryCommitContributor::~DirectoryCommitContributor() {}
 
-scoped_ptr<CommitContribution>
-DirectoryCommitContributor::GetContribution(size_t max_entries) {
+std::unique_ptr<CommitContribution> DirectoryCommitContributor::GetContribution(
+    size_t max_entries) {
   return DirectoryCommitContribution::Build(
       dir_, type_, max_entries, debug_info_emitter_);
 }
 
 }  // namespace syncer