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

components/sync/engine_impl/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 "components/sync/engine_impl/directory_commit_contributor.h"
 
-#include <stddef.h>
-
 #include "components/sync/engine_impl/cycle/directory_type_debug_info_emitter.h"
-#include "components/sync/engine_impl/directory_commit_contribution.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() {}
 
 std::unique_ptr<CommitContribution> DirectoryCommitContributor::GetContribution(
     size_t max_entries) {
   return DirectoryCommitContribution::Build(dir_, type_, max_entries,
                                             debug_info_emitter_);
 }
 
 }  // namespace syncer