Merge branch '3.4'

* 3.4: (26 commits)
  [Routing] Fix resource miss
  [Security] Fixed auth provider authenticate() cannot return void
  [FrameworkBundle][Serializer] Move DateIntervalNormalizer definition to xml
  declare argument type
  Improving annotation loader message
  [FrameworkBundle][Serializer] Move normalizer/encoders definitions to xml file & remove unnecessary checks
  Update UPGRADE-4.0.md
  streamed response should return $this
  $isClientIpsVali is not used
  [WebServerBundle] Prevent commands from being registered by convention
  content can be a resource
  Adding the Form default theme files to be warmed up in Twig's cache
  Remove BC Break label from `NullDumper` class
  Username and password in basic auth are allowed to contain '.'
  Remove obsolete PHPDoc from UriSigner
  [Serializer] YamlEncoder: throw if the Yaml component isn't installed
  [Serializer] ObjectNormalizer: throw if PropertyAccess isn't installed
  [PropertyInfo] Add support for the iterable type
  pdo session fix
  Fixed pathinfo calculation for requests starting with a question mark.  - fix bad conflict resolving issue  - port symfony/symfony#21968 to 3.3+
  ...

Author: nicolas-grekas

Crawler.php

@@ -1071,7 +1071,7 @@ public function count()
     }
 
     /**
-     * @return \ArrayIterator
+     * @return \ArrayIterator|\DOMElement[]
      */
     public function getIterator()
     {