Tests are ridiculously slow on xenial_-_edge_-_wayland

[UniversalSuperBox]

During armhf tests in the xenial_-_edge_-_wayland branch, the following can be seen:

QWARN  : qmltestrunner::Panel::test_aboutToShowMenu() [PERFORMANCE]: Last frame took 170 ms to render.
QWARN  : qmltestrunner::Panel::test_aboutToShowMenu() [PERFORMANCE]: Last frame took 174 ms to render.
QWARN  : qmltestrunner::Panel::test_aboutToShowMenu() [PERFORMANCE]: Last frame took 170 ms to render.
QWARN  : qmltestrunner::Panel::test_aboutToShowMenu() [PERFORMANCE]: Last frame took 174 ms to render.
QWARN  : qmltestrunner::Panel::test_aboutToShowMenu() [PERFORMANCE]: Last frame took 170 ms to render.
QWARN  : qmltestrunner::Panel::test_aboutToShowMenu() [PERFORMANCE]: Last frame took 183 ms to render.
QWARN  : qmltestrunner::Panel::test_aboutToShowMenu() [PERFORMANCE]: Last frame took 173 ms to render.
QWARN  : qmltestrunner::Panel::test_aboutToShowMenu() [PERFORMANCE]: Last frame took 178 ms to render.
QWARN  : qmltestrunner::Panel::test_aboutToShowMenu() [PERFORMANCE]: Last 10 frames took over 17 ms to render (last frame: 178 ms)

The same happens on amd64, but to a lesser extent:

QWARN  : qmltestrunner::Panel::test_aboutToShowMenu() [PERFORMANCE]: Last frame took 91 ms to render.
QWARN  : qmltestrunner::Panel::test_aboutToShowMenu() [PERFORMANCE]: Last frame took 89 ms to render.
QWARN  : qmltestrunner::Panel::test_aboutToShowMenu() [PERFORMANCE]: Last frame took 89 ms to render.
QWARN  : qmltestrunner::Panel::test_aboutToShowMenu() [PERFORMANCE]: Last frame took 88 ms to render.
QWARN  : qmltestrunner::Panel::test_aboutToShowMenu() [PERFORMANCE]: Last frame took 95 ms to render.
QWARN  : qmltestrunner::Panel::test_aboutToShowMenu() [PERFORMANCE]: Last frame took 90 ms to render.
QWARN  : qmltestrunner::Panel::test_aboutToShowMenu() [PERFORMANCE]: Last frame took 88 ms to render.
QWARN  : qmltestrunner::Panel::test_aboutToShowMenu() [PERFORMANCE]: Last 10 frames took over 17 ms to render (last frame: 88 ms)

This slowness is causing tests to exhibit rare and interesting race conditions. Unfortunately due to time constraints, I need to disable the tests on the slower armhf and arm64 architectures while also fixing the problems.

The issue seems to be related to Mesa in xenial_-_edge_-_wayland. If I install the Ubuntu 16.04.1 version of Mesa, the tests run more quickly again. Of course we can't use this older version of Mesa since it doesn't include a useful version of Lima for our A64 devices.

If you're interested in installing this older Mesa, first install the build-dependencies for unity8 in xenial_-edge-_wayland then run the following command:

apt install libwayland-egl1-mesa=18.0.5-0ubuntu0~16.04.1 libegl1-mesa=18.0.5-0ubuntu0~16.04.1 libgbm1=18.0.5-0ubuntu0~16.04.1 libgl1-mesa-dri=18.0.5-0ubuntu0~16.04.1 libegl1-mesa-dev=18.0.5-0ubuntu0~16.04.1 libwayland-dev=1.12.0-1~ubuntu16.04.3 libwayland-client0=1.12.0-1~ubuntu16.04.3 libwayland-server0=1.12.0-1~ubuntu16.04.3 libwayland-cursor0=1.12.0-1~ubuntu16.04.3 libwayland-bin=1.12.0-1~ubuntu16.04.3 libgl1-mesa-dev=18.0.5-0ubuntu0~16.04.1 mesa-common-dev=18.0.5-0ubuntu0~16.04.1 libgl1-mesa-glx=18.0.5-0ubuntu0~16.04.1 libglapi-mesa=18.0.5-0ubuntu0~16.04.1 unity8-build-deps libgles2-mesa-dev=18.0.5-0ubuntu0~16.04.1 libgles2-mesa=18.0.5-0ubuntu0~16.04.1