Leave out empty-valued Access-Control-Request-Headers: on preflights.

third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/fetch-access-control.php

 <?php
 header('X-ServiceWorker-ServerHeader: SetInTheServer');
 
 $prefix = '';
 // If PreflightTest is set:
 // - Use PACAOrign, PACAHeaders, PACAMethods, PACACredentials, PACEHeaders,
 //   PAuth, PAuthFail and PSetCookie* parameters in preflight.
 // - Use $_GET['PreflightTest'] as HTTP status code.
 // - Check Access-Control-Request-Method/Headers headers with
 //   PACRMethod/Headers parameter, if set, in preflight.
+//   The special value 'missing' for PACRHeaders can be used to
+//   test for the absence of ACRHeaders on the preflight request.
 if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS' && isset($_GET['PreflightTest'])) {
     $prefix = 'P';
 
     if (isset($_GET['PACRMethod']) &&
         $_GET['PACRMethod'] !=
         $_SERVER['HTTP_ACCESS_CONTROL_REQUEST_METHOD']) {
         header("HTTP/1.1 400");
         exit;
     }
-    if (isset($_GET['PACRHeaders']) &&
-        $_GET['PACRHeaders'] !=
-        $_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']) {
-        header("HTTP/1.1 400");
-        exit;
+    if (isset($_GET['PACRHeaders'])) {
+       if ($_GET['PACRHeaders'] == 'missing') {
+           if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS'])) {
+               header("HTTP/1.1 400");
+               exit;
+           }
+       } else if ($_GET['PACRHeaders'] !=
+                  $_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']) {
+           header("HTTP/1.1 400");
+           exit;
+       }
     }
     // Preflight must not include Cookie headers.
     if (isset($_SERVER['HTTP_COOKIE'])) {
         header("HTTP/1.1 400");
         exit;
     }
     header("HTTP/1.1 {$_GET['PreflightTest']}");
 }
 
 if (isset($_GET[$prefix . 'ACAOrigin'])) {
@@ skipping 67 matching lines @@
              'headers' => getallheaders(),
              'body' => file_get_contents('php://input'),
              'files' => $files,
              'get' => $_GET,
              'post' => $_POST,
              'username' => $username,
              'password' => $password,
              'cookie' => $cookie);
 $json = json_encode($arr);
 echo "report( $json );";
-?>
+?>