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diff --git a/vendor/symfony/http-kernel/HttpCache/ResponseCacheStrategy.php b/vendor/symfony/http-kernel/HttpCache/ResponseCacheStrategy.php
new file mode 100644
index 000000000..39a99e696
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+++ b/vendor/symfony/http-kernel/HttpCache/ResponseCacheStrategy.php
@@ -0,0 +1,93 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * This code is partially based on the Rack-Cache library by Ryan Tomayko,
+ * which is released under the MIT license.
+ * (based on commit 02d2b48d75bcb63cf1c0c7149c077ad256542801)
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\HttpKernel\HttpCache;
+
+use Symfony\Component\HttpFoundation\Response;
+
+/**
+ * ResponseCacheStrategy knows how to compute the Response cache HTTP header
+ * based on the different response cache headers.
+ *
+ * This implementation changes the master response TTL to the smallest TTL received
+ * or force validation if one of the surrogates has validation cache strategy.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+class ResponseCacheStrategy implements ResponseCacheStrategyInterface
+{
+    private $cacheable = true;
+    private $embeddedResponses = 0;
+    private $ttls = array();
+    private $maxAges = array();
+    private $isNotCacheableResponseEmbedded = false;
+
+    /**
+     * {@inheritdoc}
+     */
+    public function add(Response $response)
+    {
+        if ($response->isValidateable()) {
+            $this->cacheable = false;
+        } else {
+            $maxAge = $response->getMaxAge();
+            $this->ttls[] = $response->getTtl();
+            $this->maxAges[] = $maxAge;
+
+            if (null === $maxAge) {
+                $this->isNotCacheableResponseEmbedded = true;
+            }
+        }
+
+        ++$this->embeddedResponses;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function update(Response $response)
+    {
+        // if we have no embedded Response, do nothing
+        if (0 === $this->embeddedResponses) {
+            return;
+        }
+
+        // Remove validation related headers in order to avoid browsers using
+        // their own cache, because some of the response content comes from
+        // at least one embedded response (which likely has a different caching strategy).
+        if ($response->isValidateable()) {
+            $response->setEtag(null);
+            $response->setLastModified(null);
+            $this->cacheable = false;
+        }
+
+        if (!$this->cacheable) {
+            $response->headers->set('Cache-Control', 'no-cache, must-revalidate');
+
+            return;
+        }
+
+        $this->ttls[] = $response->getTtl();
+        $this->maxAges[] = $response->getMaxAge();
+
+        if ($this->isNotCacheableResponseEmbedded) {
+            $response->headers->removeCacheControlDirective('s-maxage');
+        } elseif (null !== $maxAge = min($this->maxAges)) {
+            $response->setSharedMaxAge($maxAge);
+            $response->headers->set('Age', $maxAge - min($this->ttls));
+        }
+        $response->setMaxAge(0);
+    }
+}