bug symfony#23586 Fix case sensitive sameSite cookie (mikefrancis)

This PR was submitted for the master branch but it was merged into the 3.2 branch instead (closes symfony#23586).

Discussion
----------

Fix case sensitive sameSite cookie

| Q             | A
| ------------- | ---
| Branch?       | 3.3
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | symfony#23585
| License       | MIT
| Doc PR        |

Commits
-------

14c310f Fix case sensitive sameSite cookie

Author: fabpot

src/Symfony/Component/HttpFoundation/Cookie.php

@@ -77,6 +77,10 @@ public function __construct($name, $value = null, $expire = 0, $path = '/', $dom
         $this->httpOnly = (bool) $httpOnly;
         $this->raw = (bool) $raw;
 
+        if (null !== $sameSite) {
+            $sameSite = strtolower($sameSite);
+        }
+
         if (!in_array($sameSite, array(self::SAMESITE_LAX, self::SAMESITE_STRICT, null), true)) {
             throw new \InvalidArgumentException('The "sameSite" parameter value is not valid.');
         }

src/Symfony/Component/HttpFoundation/Tests/CookieTest.php

@@ -180,4 +180,10 @@ public function testRawCookie()
         $this->assertTrue($cookie->isRaw());
         $this->assertEquals('foo=b+a+r; path=/', (string) $cookie);
     }
+
+    public function testSameSiteAttributeIsCaseInsensitive()
+    {
+        $cookie = new Cookie('foo', 'bar', 0, '/', null, false, true, false, 'Lax');
+        $this->assertEquals('lax', $cookie->getSameSite());
+    }
 }