Translator component has default domain for null implemented

no need to have default translation domain logic in 3 different places

src/Symfony/Bridge/Twig/Extension/TranslationExtension.php

@@ -90,19 +90,11 @@ class TranslationExtension extends \Twig_Extension
 
     public function trans($message, array $arguments = array(), $domain = null, $locale = null)
     {
-        if (null === $domain) {
-            $domain = 'messages';
-        }
-
         return $this->translator->trans($message, $arguments, $domain, $locale);
     }
 
     public function transchoice($message, $count, array $arguments = array(), $domain = null, $locale = null)
     {
-        if (null === $domain) {
-            $domain = 'messages';
-        }
-
         return $this->translator->transChoice($message, $count, array_merge(array('%count%' => $count), $arguments), $domain, $locale);
     }
 

src/Symfony/Component/Form/Extension/Core/Type/BaseType.php

@@ -56,7 +56,7 @@ abstract class BaseType extends AbstractType
                 $uniqueBlockPrefix = '_'.$blockName;
             }
 
-            if (!$translationDomain) {
+            if (null === $translationDomain) {
                 $translationDomain = $view->parent->vars['translation_domain'];
             }
         } else {
@@ -76,10 +76,6 @@ abstract class BaseType extends AbstractType
         }
         $blockPrefixes[] = $uniqueBlockPrefix;
 
-        if (!$translationDomain) {
-            $translationDomain = 'messages';
-        }
-
         $view->vars = array_replace($view->vars, array(
             'form' => $view,
             'id' => $id,

src/Symfony/Component/Form/Tests/Extension/Core/Type/BaseTypeTest.php

@@ -112,7 +112,7 @@ abstract class BaseTypeTest extends \Symfony\Component\Form\Test\TypeTestCase
             ->getForm()
             ->createView();
 
-        $this->assertEquals('messages', $view['child']->vars['translation_domain']);
+        $this->assertNull($view['child']->vars['translation_domain']);
     }
 
     public function testPassLabelToView()