Rewrite scoped_ptr<T>(NULL) to use the default ctor in sync/.

sync/syncable/directory_backing_store.cc

 // Copyright 2012 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/syncable/directory_backing_store.h"
 
 #include "build/build_config.h"
 
 #include <limits>
 
@@ skipping 90 matching lines @@
     kernel->mutable_ref(static_cast<ProtoField>(i)).ParseFromArray(
         statement->ColumnBlob(i), statement->ColumnByteLength(i));
   }
   for ( ; i < UNIQUE_POSITION_FIELDS_END; ++i) {
     std::string temp;
     statement->ColumnBlobAsString(i, &temp);
 
     sync_pb::UniquePosition proto;
     if (!proto.ParseFromString(temp)) {
       DVLOG(1) << "Unpacked invalid position.  Assuming the DB is corrupt";
-      return scoped_ptr<EntryKernel>(NULL);
+      return scoped_ptr<EntryKernel>();
     }
 
     kernel->mutable_ref(static_cast<UniquePositionField>(i)) =
         UniquePosition::FromProto(proto);
   }
   return kernel.Pass();
 }
 
 namespace {
 
@@ skipping 1370 matching lines @@
   }
   query.append(" ) ");
   values.append(" )");
   query.append(values);
   save_statement->Assign(db_->GetUniqueStatement(
       base::StringPrintf(query.c_str(), "metas").c_str()));
 }
 
 }  // namespace syncable
 }  // namespace syncer