Bug 249367

Description:
imported/w3c/web-platform-tests/html/canvas/offscreen/manual/the-offscreen-canvas/offscreencanvas.transferrable.w.html

The test was added at 257673@main and has been a flaky failure since then.

This issue can be bisected to 257673@main using command:
run-webkit-tests --release -f --clobber-old-results --exit-after-n-failures 1  --force  --child-processes=5 --iterations=50  --ios-simulator  imported/w3c/web-platform-tests/html/canvas/offscreen/manual/the-offscreen-canvas/offscreencanvas.transferrable.w.html

History:
https://results.webkit.org/?suite=layout-tests&test=imported%2Fw3c%2Fweb-platform-tests%2Fhtml%2Fcanvas%2Foffscreen%2Fmanual%2Fthe-offscreen-canvas%2Foffscreencanvas.transferrable.w.html&platform=ios

Diff:
@@ -1,7 +1,9 @@
+
+Harness Error (TIMEOUT), message = null

 PASS Test that OffscreenCanvas's size is correct after being transferred from a worker.
 PASS Test that transfer an OffscreenCanvas that has a 2d context throws exception in a worker.
-PASS Test that transfer an OffscreenCanvas that has a webgl context throws exception in a worker.
+TIMEOUT Test that transfer an OffscreenCanvas that has a webgl context throws exception in a worker. Test timed out
 PASS Test that transfer an OffscreenCanvas twice throws exception in a worker.
 PASS Test that calling getContext('2d') on a detached OffscreenCanvas throws exception in a worker.
 PASS Test that calling getContext('webgl') on a detached OffscreenCanvas throws exception in a worker.