The following layout test is flaky on Windows

virtual/mojo-service-worker/http/tests/serviceworker/foreign-fetch-cors.html

See https://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=virtual%2Fmojo-service-worker%2Fhttp%2Ftests%2Fserviceworker%2Fforeign-fetch-cors.html

In addition, despite automatic retries it sometimes turns the build red: https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Win7%20(dbg)/builds/7814

When it fails, the output is:

CONSOLE ERROR: line 106: Refused to get unsafe header "X-ServiceWorker-ServerHeader"
CONSOLE ERROR: line 106: Refused to get unsafe header "X-ServiceWorker-ServerHeader"
CONSOLE ERROR: line 106: Refused to get unsafe header "X-ServiceWorker-ServerHeader"
CONSOLE ERROR: line 106: Refused to get unsafe header "X-ServiceWorker-ServerHeader"
This is a testharness.js-based test.
Harness Error. harness_status.status = 2 , harness_status.message = null
PASS Same origin fetch without CORS headers, not exposed 
PASS Same origin fetch without CORS headers, only origin exposed 
PASS Same origin fetch without CORS headers, headers and origin exposed 
PASS Same origin fetch without CORS headers, exposed to wrong origin 
PASS Same origin fetch with CORS headers, not exposed 
PASS Same origin fetch with CORS headers, only origin exposed 
PASS Same origin fetch with CORS headers, headers and origin exposed 
PASS Same origin fetch with CORS headers, exposed to wrong origin 
PASS Cross origin fetch without CORS headers, not exposed 
PASS Cross origin fetch with ACEHeaders header, not exposed 
PASS Cross origin fetch with ACEHeaders header, only origin exposed 
PASS Cross origin fetch with ACEHeaders header, headers and origin exposed 
PASS Cross origin fetch with ACEHeaders header, exposed to wrong origin 
PASS Cross origin fetch without ACEHeaders header, not exposed 
PASS Cross origin fetch without ACEHeaders header, only origin exposed 
TIMEOUT Cross origin fetch without ACEHeaders header, headers and origin exposed Test timed out
Harness: the test ran to completion.