It seems that this is a flaky test:

- It usually passes locally with a Release build.  OTOH, I've seen it fail in Release build both with --site-per-process and without this flag.

- It seems to fail more often in Debug build.

- It seems that the very next linux_site_isolation build is green: https://build.chromium.org/p/chromium.fyi/builders/Site%20Isolation%20Linux/builds/8494

Thanks lukasza@!  Yep, this is failing on other bots as well:
https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Mac10.11/builds/1234
https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux/builds/62333

Found via Flakiness dashboard:
http://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=http%2Ftests%2FlinkHeader%2Flink-preload-in-iframe.html

Yoav, should this get reverted until the flakiness is resolved?

I have a speculative attempt to unflake that test at https://codereview.chromium.org/1827773002/

If that fails, I prefer to mark it as a flake in expectations rather than revert the CL, as the CL changes are not the cause of flakiness.

I've added japhet@ to that review, since it doesn't look to me like it will help.

In the meantime, can you mark the test flaky?  It's failing frequently now.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/69e8ba23ef353ca5a06d2d9acd9da50ace03da28

commit 69e8ba23ef353ca5a06d2d9acd9da50ace03da28
Author: yoav <yoav@yoav.ws>
Date: Thu Mar 24 16:43:08 2016

Speculative attempt to unflake preload iframe test

https://codereview.chromium.org/1738133002 landed an iframe test for preload,
which seems to be slightly flaky. This is an attempt to unflake the test
by increasing its timeout.

BUG= 597097 

Review URL: https://codereview.chromium.org/1827773002

Cr-Commit-Position: refs/heads/master@{#383077}

[modify] https://crrev.com/69e8ba23ef353ca5a06d2d9acd9da50ace03da28/third_party/WebKit/LayoutTests/http/tests/linkHeader/resources/iframe-link-headers.php

Haven't seen any failures since.  Thanks!