There are missing initialization steps for Ozone Chrome OS tests that run with --ozone-platform=x11. In particular, a test only initialization step to change override redirect X parameter is missing.

I noticed this when running views_mus_interactive_ui_tests locally with Xvfb. The test passes the first time it is run. The test fails if it is run again. If the binary gets replaced, the test will pass once. This doesn't occur running without Xvfb.

$ ninja -C out_test/release views_mus_interative_ui_tests
$ python testing/xvfb.py out_test/release/views_mus_interactive_ui_tests
# works
$ python testing/xvfb.py out_test/release/views_mus_interactive_ui_tests
# hangs and eventually times out
$ rm out_test/release/views_mus_interative_ui_tests
$ ninja -C out_test/release views_mus_interative_ui_tests
$ python testing/xvfb.py out_test/release/views_mus_interactive_ui_tests
# works again

The problem occurs when an XWindow is created and initialization blocks until a Map XEvent is received. The XEvent doesn't arrive and the test blocks until it times out.

This is related to ui::test::SetUseOverrideRedirectWindowByDefault() which changes one of the arguments to XCreateWindow(). In some test fixtures there is a block like:

#if defined(USE_X11)
 ui::test::SetUseOverrideRedirectWindowByDefault(true);
#endif

https://cs.chromium.org/chromium/src/ui/aura/test/aura_test_helper.cc?type=cs&l=55

This never gets called for Ozone X11 because USE_X11=0. Since the Ozone platform is decided at runtime it's not quite as simple. It will probably require adding a virtual function to OzonePlatform.