Fix http/tests/cache random-order flakiness

third_party/WebKit/LayoutTests/http/tests/cache/resources/post-image-to-verify.php

 <?php
 require_once '../../resources/portabilityLayer.php';
 
 clearstatcache();
-if (file_exists(sys_get_temp_dir() . "/post.tmp")) {
+$tmpFilename = sys_get_temp_dir() . "/" . $_GET['filename'];
+if (file_exists($tmpFilename)) {
     header('HTTP/1.1 404 Not Found');
     exit();
 } else {
-    $tmpFile = fopen(sys_get_temp_dir() . "/post.tmp", 'w');
+    $tmpFile = fopen($tmpFilename, 'w');
     fclose($tmpFile);
     
     $filename = 'compass-no-cache.jpg';
     $filemtime = filemtime($filename);
     $filesize = filesize($filename);
 
     $etag = '"' . $filesize . '-' . $filemtime . '"';
     $last_modified = gmdate(DATE_RFC1123, $filemtime);
     $max_age = 12 * 31 * 24 * 60 * 60; //one year
     $expires = gmdate(DATE_RFC1123, time() + $max_age);
 
     $handle = fopen($filename, 'rb');
     $contents = fread($handle, $filesize);
     fclose($handle);
 
     header('Cache-Control: public, max-age=' . $max_age);
     header('Expires: ' . $expires);
     header('Content-Type: image/png');
     header('Content-Length: ' . $filesize);
     header('Etag: ' . $etag);
     header('Last-Modified: ' . $last_modified);
     echo $contents;
     exit();
 }
 ?>