Bug 218716

Created attachment 413601 [details]
Imgdiff of first failed run

mathml/presentation/non-bmp-operators-stretching.html

The test operators are not stretched in the prefix form when it is the first of its kind run, likely missing some kind of initialization. For example, running 3 iterations, the first one fails and the other 2 work fine. But with `--run-singly`, it fails in all 3 iterations.

Running the non-bmp-operators-spacing test before it also makes the test pass.

A similar behavior happens in MiniBrowser:

- Load mathml/presentation/non-bmp-operators-stretching.html. Not stretched
- Load mathml/presentation/non-bmp-operators-stretching-expected.html (or the spacing version)
- Navigate back to mathml/presentation/non-bmp-operators-stretching.html - Stretched
- A full reload brings back the failure.

I noticed this while investigating the failure in a WPE build[1], likely due to being run after a worker crash.

[1] https://build.webkit.org/results/WPE-Linux-64-bit-Release-Tests/r269580%20(20968)/results.html

Attached is the img diff of the failure. Some letters diff but only in its vertical position, due to the operator height.

As this is kinda corner case, I'll not update the expectations to avoid hiding eventual more reproducible failures.