Add layout tests about sendBeacon's handling of credentials for cross origin redirects

third_party/WebKit/LayoutTests/http/tests/navigation/resources/save-beacon.php

 <?php
 require_once '../../resources/portabilityLayer.php';
 
 function prettify($name) {
    return str_replace(' ', '-', ucwords(str_replace('_', ' ', str_replace('http_', '', strtolower($name)))));
 }
 
 $beaconFilename = sys_get_temp_dir() . "/beacon" . (isset($_REQUEST['name']) ? $_REQUEST['name'] : "") . ".txt";
 $beaconFile = fopen($beaconFilename . ".tmp", 'w');
 $httpHeaders = $_SERVER;
@@ skipping 14 matching lines @@
    $postdata = http_build_query($_POST);
 
 fwrite($beaconFile, "Length: " . strlen($postdata) . "\n");
 if (strpos($contentType, "application/") !== false) {
     $postdata = base64_encode($postdata);
 }
 
 fwrite($beaconFile, "Body: $postdata\n");
 fclose($beaconFile);
 rename($beaconFilename . ".tmp", $beaconFilename);
-foreach ($_COOKIE as $name => $value)
-    setcookie($name, "deleted", time() - 60, "/");
+
+if (!array_key_exists('dontclearcookies', $_GET)) {
+  foreach ($_COOKIE as $name => $value)
+      setcookie($name, "deleted", time() - 60, "/");
+}
 ?>