Revalidation header blacklisting should be case-insensitive.

LayoutTests/http/tests/cache/resources/stylesheet304-bad-content-type.php

Index: LayoutTests/http/tests/cache/resources/stylesheet304-bad-content-type.php
diff --git a/LayoutTests/http/tests/cache/resources/stylesheet304-bad-content-type.php b/LayoutTests/http/tests/cache/resources/stylesheet304-bad-content-type.php
new file mode 100644
index 0000000000000000000000000000000000000000..2adf6c8279e664ea1cb6f0d031c0dfde26219cee
--- /dev/null
+++ b/LayoutTests/http/tests/cache/resources/stylesheet304-bad-content-type.php
@@ -0,0 +1,21 @@
+<?php
+require_once '../../resources/portabilityLayer.php';
+
+clearstatcache();
+
+if ($_SERVER["HTTP_IF_MODIFIED_SINCE"]) {
+    header("HTTP/1.0 304 Not Modified");
+    header("Content-Type: text/plain");
+    exit();
+}
+$one_year = 12 * 31 * 24 * 60 * 60;
+$last_modified = gmdate(DATE_RFC1123, time() - $one_year);
+$expires = gmdate(DATE_RFC1123, time() + $one_year);
+
+header('Cache-Control: public, max-age=' . $one_year);
+header('Expires: ' . $expires);
+header('Content-Type: text/css');
+header('Etag: 123456789');
+header('Last-Modified: ' . $last_modified);
+?>
+#test { background-color: rgb(0, 255, 0); }