@chrishtr Looks like this test still times out on Firefox and Chrome. Would you mind taking a second look?

Will try to repro now.

If it helps, I can reproduce on a fresh checkout of WPT via:

$ git checkout chromium-export-bb6643e9d8
$ ./wpt run --log-mach-level=info --log-mach=- --verify --verify-log-full --channel=experimental chrome html/semantics/embedded-content/the-img-element/image-loading-subpixel-clip.html 
...
 1:29.90 INFO ## Unstable results ##

 1:29.90 INFO |                                         Test                                        | Subtest |            Results            | Messages |
 1:29.90 INFO |-------------------------------------------------------------------------------------|---------|-------------------------------|----------|
 1:29.90 INFO | `/html/semantics/embedded-content/the-img-element/image-loading-subpixel-clip.html` |         | **PASS: 6/10, TIMEOUT: 4/10** |          |

Looking at the test - does target.onload fire even if the target has already loaded (if that is possible) when that script executes?

EDIT: if you want to pass a specific chrome binary in, you can pass the --binary=/path/to/chrome flag to wpt run. Note that you still need to set the 'product' as chrome, e.g. it looks like:

./wpt run --binary=/path/to/chrome --log-mach-level=info --log-mach=- --verify --verify-log-full --channel=experimental chrome html/semantics/embedded-content/the-img-element/image-loading-subpixel-clip.html

@stephenmcgruer I think you figured it out thanks. I reproduced the flakiness locally and I think
fixed it by setting the src attribute after adding the onload handler. I'll make a Chromium patch
now.

Glad to hear it. Admin-merging this so that the following patch can be successfully exported. Note that you can check on the stabiltity checks/etc before merging a patch Chromium side. After sending it out for review look for the wpt-pr-bot to comment on it saying its been uploaded to GH (should contain a link to the PR) :).