769659 - adding some new reftests can break following tests due to "stuck" canvases

Status: NEW

(Testing :: Reftest, defect)

Description

[Jonathan Kew [:jfkthame]]

I wonder if this is a manifestation of something similar to bug 384631 (or even a dupe), but that's been dormant for long enough that maybe we need to take a fresh look. The logs at

  https://tbpl.mozilla.org/?tree=Try&rev=9149c51a5250

such as for example

  https://tbpl.mozilla.org/php/getParsedLog.php?id=13103403&tree=Try

show 129 failures on Linux64, but not on other platforms (the individual failures of some font-matching/bold-system-fallback-* tests are expected).

Viewing the log in reftest analyzer, it appears that canvases from the newly-added (and random-on-linux) testcases are being used in place of the proper test or reference in the following tests, leading to massive fail.