What steps will reproduce the problem?

(1) Check CQ dry run results of https://chromium-review.googlesource.com/c/chromium/src/+/1033430/7

(2) Inspect any of the failed builds. For example:
https://ci.chromium.org/p/chromium/builders/luci.chromium.try/mac_chromium_rel_ng/141840

(3) Check the layout test results page:
https://test-results.appspot.com/data/layout_results/mac_chromium_rel_ng/141840/layout-test-results/results.html

What is the expected result?

The results page delivers all test results, and shows details of failed test.

What happens instead?

The results page delivers only one test result, where the failed test is shown as PASS.