<select ng-model="filtro.galpao" chosen id="BuscarGalpaoId">
  <option selected="selected" value="">Selecione um Galpão</option>
  <option ng-repeat="galpao in selectList.galpoes"
    ng-class="{
      incompleto: galpao.situacao === 'incompleto',
      completo: galpao.situacao === 'completo',
      vazio: galpao.situacao === 'vazio',
      inativo: galpao.situacao === 'inativo'
    }" value="{{galpao.id}}">{{galpao.descricao}}
  </option>
</select>

app.directive('chosen', function ($timeout) {
    var linker = function (scope, elemen, attrs) {
        // update the select when data is loaded
        scope.$watch(attrs.select2, function (oldVal, newVal) {
            $timeout(function () {
                elemen.trigger('change');
            }, 100);
        });

        // update the select when the model changes
        scope.$watch(attrs.ngModel, function () {
            $timeout(function () {
                elemen.trigger('change');
            }, 100);
        });

        angular.element(elemen).select2({width: '100%'});
    };

    return {
        restrict: 'A',
        link: linker
    };
});