Mark flaky CORS keepalive tests possibly caused by insufficient timeout

Bug: 1455180

Change-Id: I294f2f8bb43edf0ddcd9ef08f669dd57cf789d5a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4672307
Commit-Queue: Ming-Ying Chung <mych@chromium.org>
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1167285}
diff --git a/fetch/api/cors/cors-keepalive.any.js b/fetch/api/cors/cors-keepalive.any.js
index 2df0c08..f68d90e 100644
--- a/fetch/api/cors/cors-keepalive.any.js
+++ b/fetch/api/cors/cors-keepalive.any.js
@@ -1,4 +1,5 @@
 // META: global=window
+// META: timeout=long
 // META: title=Fetch API: keepalive handling
 // META: script=/resources/testharness.js
 // META: script=/resources/testharnessreport.js