Deflake http/tests/navigation/ping-*.

LayoutTests/http/tests/navigation/resources/save-Ping.php

Index: LayoutTests/http/tests/navigation/resources/save-Ping.php
diff --git a/LayoutTests/http/tests/navigation/resources/save-Ping.php b/LayoutTests/http/tests/navigation/resources/save-Ping.php
index d818de93f9195ec7309653df38d685487dde8212..08be62950b6b31bc36143883142179bf3816f780 100644
--- a/LayoutTests/http/tests/navigation/resources/save-Ping.php
+++ b/LayoutTests/http/tests/navigation/resources/save-Ping.php
@@ -9,7 +9,8 @@ foreach ($httpHeaders as $name => $value) {
         fwrite($pingFile, "$name: $value\n");
 }
 fclose($pingFile);
-rename(sys_get_temp_dir() . "/ping.txt.tmp", sys_get_temp_dir() . "/ping.txt");
+$finalPingFilename = sys_get_temp_dir() . "/ping." . $_GET["test"];
+rename(sys_get_temp_dir() . "/ping.txt.tmp", $finalPingFilename);
 foreach ($_COOKIE as $name => $value)
     setcookie($name, "deleted", time() - 60, "/");
 ?>