Merge branch '2.8' into 3.4

* 2.8:
  Fix CS
  Allow reuse of Session between requests
  Provide debug_backtrace with proper args
  forward false label option to nested types
  forward the invalid_message option in date types

Author: nicolas-grekas

Tests/DependencyInjection/CompleteConfigurationTest.php

@@ -173,8 +173,8 @@ public function testFirewalls()
                 null,
                 null,
                 array(
-                  'simple_form',
-                  'anonymous',
+                    'simple_form',
+                    'anonymous',
                 ),
                 null,
             ),