Merge branch '3.1'

* 3.1:
  [travis] Don't use parallel on HHVM
  [HttpKernel] Fix RequestDataCollector starting the session
  [appveyor] Ignore STATUS_HEAP_CORRUPTION errors on Windows
  [FrameworkBundle] Skip redis cache pools test on failed connection
  Fixed forwarded request data in templates
  [Security] Fix DebugAccessDecisionManager when object is not a scalar
  Skip some tests on HHVM due to a PHPunit bug
  Use the Trusty Travis infrastructure for HHVM builds
  LdapUserProvider: add missing argument type doc
  Fixed issue with missing argument in the abstract service definition for the ldap user provider
  Add 3.1 to  PR template branch row, remove 2.3
  Improve memory efficiency
  [Console] Fix BC break introduced by #18101
  document method name changes in Voter class
  add missing hint for vote() argument type
  [#18838] add a test to avoid regressions
  bumped Symfony version to 3.1.1
  updated VERSION for 3.1.0
  updated CHANGELOG for 3.1.0

Conflicts:
	src/Symfony/Component/HttpKernel/Kernel.php

Author: nicolas-grekas

DataCollector/RequestDataCollector.php

@@ -130,7 +130,7 @@ public function collect(Request $request, Response $response, \Exception $except
             unset($this->controllers[$request]);
         }
 
-        if (null !== $session) {
+        if (null !== $session && $session->isStarted()) {
             if ($request->attributes->has('_redirected')) {
                 $this->data['redirect'] = $session->remove('sf_redirect');
             }
@@ -291,7 +291,7 @@ public function onKernelController(FilterControllerEvent $event)
 
     public function onKernelResponse(FilterResponseEvent $event)
     {
-        if (!$event->isMasterRequest() || !$event->getRequest()->hasSession()) {
+        if (!$event->isMasterRequest() || !$event->getRequest()->hasSession() || !$event->getRequest()->getSession()->isStarted()) {
             return;
         }
 

Tests/DataCollector/DumpDataCollectorTest.php

@@ -113,7 +113,7 @@ public function testFlush()
         $line = __LINE__ - 1;
 
         ob_start();
-        $collector = null;
+        $collector->__destruct();
         $this->assertSame("DumpDataCollectorTest.php on line {$line}:\n456\n", ob_get_clean());
     }
 }

Tests/DataCollector/RequestDataCollectorTest.php

@@ -11,7 +11,10 @@
 
 namespace Symfony\Component\HttpKernel\Tests\DataCollector;
 
+use Symfony\Component\HttpFoundation\Session\Session;
+use Symfony\Component\HttpFoundation\Session\Storage\MockArraySessionStorage;
 use Symfony\Component\HttpKernel\Controller\ArgumentResolverInterface;
+use Symfony\Component\HttpKernel\Event\FilterResponseEvent;
 use Symfony\Component\HttpKernel\HttpKernel;
 use Symfony\Component\HttpKernel\HttpKernelInterface;
 use Symfony\Component\HttpKernel\DataCollector\RequestDataCollector;
@@ -52,6 +55,20 @@ public function testCollect()
         $this->assertSame('application/json', $c->getContentType());
     }
 
+    public function testKernelResponseDoesNotStartSession()
+    {
+        $kernel = $this->getMock(HttpKernelInterface::class);
+        $request = new Request();
+        $session = new Session(new MockArraySessionStorage());
+        $request->setSession($session);
+        $response = new Response();
+
+        $c = new RequestDataCollector();
+        $c->onKernelResponse(new FilterResponseEvent($kernel, $request, HttpKernelInterface::MASTER_REQUEST, $response));
+
+        $this->assertFalse($session->isStarted());
+    }
+
     /**
      * Test various types of controller callables.
      */