Merge branch '2.8' into 3.3

* 2.8:
  [HttpFoundation] Fix forward-compat of NativeSessionStorage with PHP 7.2

Author: nicolas-grekas

src/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php

@@ -102,6 +102,12 @@ class NativeSessionStorage implements SessionStorageInterface
      */
     public function __construct(array $options = array(), $handler = null, MetadataBag $metaBag = null)
     {
+        $this->setMetadataBag($metaBag);
+
+        if (\PHP_SESSION_ACTIVE === session_status()) {
+            return;
+        }
+
         $options += array(
             // disable by default because it's managed by HeaderBag (if used)
             'cache_limiter' => '',
@@ -110,7 +116,6 @@ public function __construct(array $options = array(), $handler = null, MetadataB
 
         session_register_shutdown();
 
-        $this->setMetadataBag($metaBag);
         $this->setOptions($options);
         $this->setSaveHandler($handler);
     }

src/Symfony/Component/HttpFoundation/Tests/Session/Storage/NativeSessionStorageTest.php

@@ -242,4 +242,24 @@ public function testRestart()
         $this->assertSame($id, $storage->getId(), 'Same session ID after restarting');
         $this->assertSame(7, $storage->getBag('attributes')->get('lucky'), 'Data still available');
     }
+
+    public function testCanCreateNativeSessionStorageWhenSessionAlreadyStarted()
+    {
+        session_start();
+        $this->getStorage();
+
+        // Assert no exception has been thrown by `getStorage()`
+        $this->addToAssertionCount(1);
+    }
+
+    public function testSetSessionOptionsOnceSessionStartedIsIgnored()
+    {
+        session_start();
+        $this->getStorage(array(
+            'name' => 'something-else',
+        ));
+
+        // Assert no exception has been thrown by `getStorage()`
+        $this->addToAssertionCount(1);
+    }
 }