minor symfony#20421 Twig deprecation removal (fabpot)

This PR was merged into the 2.7 branch.

Discussion
----------

Twig deprecation removal

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

Commits
-------

eb0d6c9 removed a deprecation notice

Author: fabpot

src/Symfony/Bridge/Twig/NodeVisitor/TranslationDefaultDomainNodeVisitor.php

@@ -49,7 +49,7 @@ protected function doEnterNode(\Twig_Node $node, \Twig_Environment $env)
 
                 return $node;
             } else {
-                $var = $env->getParser()->getVarName();
+                $var = $this->getVarName();
                 $name = new \Twig_Node_Expression_AssignName($var, $node->getTemplateLine());
                 $this->scope->set('domain', new \Twig_Node_Expression_Name($var, $node->getTemplateLine()));
 
@@ -123,4 +123,9 @@ private function isNamedArguments($arguments)
 
         return false;
     }
+
+    private function getVarName()
+    {
+        return sprintf('__internal_%s', hash('sha256', uniqid(mt_rand(), true), false));
+    }
 }