Merge branch '3.1'

* 3.1:
  [VarDumper] Fix dumping jsons casted as arrays
  PassConfig::getMergePass is not an array
  Revert "bug #19114 [HttpKernel] Dont close the reponse stream in debug (nicolas-grekas)"
  [Serializer] Include the format in the cache key
  Fix the retrieval of the last username when using forwarding
  [Yaml] Fix PHPDoc of the Yaml class
  [HttpFoundation] Add OPTIONS and TRACE to the list of safe methods
  Update getAbsoluteUri() for query string uris

Conflicts:
	src/Symfony/Component/DependencyInjection/Compiler/PassConfig.php
	src/Symfony/Component/HttpFoundation/Tests/RequestTest.php

Author: nicolas-grekas

Compiler/PassConfig.php

@@ -166,7 +166,7 @@ public function getRemovingPasses()
     }
 
     /**
-     * Gets all passes for the Merge pass.
+     * Gets the Merge pass.
      *
      * @return CompilerPassInterface
      */