Fix http/tests/cache random-order flakiness

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

Index: third_party/WebKit/LayoutTests/http/tests/cache/resources/post-image-to-verify.php
diff --git a/third_party/WebKit/LayoutTests/http/tests/cache/resources/post-image-to-verify.php b/third_party/WebKit/LayoutTests/http/tests/cache/resources/post-image-to-verify.php
index d3abe0d080709ce8cd46684376c93449aa3fd99b..2ddd8fcbe2c15db80d174e272b5c26e5ec3eefbe 100644
--- a/third_party/WebKit/LayoutTests/http/tests/cache/resources/post-image-to-verify.php
+++ b/third_party/WebKit/LayoutTests/http/tests/cache/resources/post-image-to-verify.php
@@ -2,11 +2,12 @@
 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';