The top menu bar is present in GNOME desktop environment by default, and this includes the docker image used in the ubuntu1804 tests currently. An example screenshot from a failed run of mochitest-e10s-5 is attached showing this.

The current environment running ubuntu1604 has no dock or top bar, meaning the browser window can make full use of the 1600x1200 resolution.

Objectives:

• remove the top menu bar from the docker image

I don't think we should fake an environment without the menu bar. Users will have one most of the time, except when using something else than GNOME.

I'll add that if the presence of the menu bar breaks some tests, then there's a problem with the tests, as that also means the test would fail if run locally.

The ubuntu1604 environment does not have a top bar or a dock currently.

I was not part of that setup work, so I don't know for certain, but perhaps it was removed at some point?

It was not removed. We weren't actually running the desktop environment, only the window manager. That it was not there was a side effect.

I suspect that the presence of the top menu bar is causing some issues with tests that hardcode a pixel value for the element, window size, etc.

As it stands the number of suspected failures from the presence of top menu bar is manageable, and if marionette window positioning issues can be worked out then there might be no need to remove the bar, though I'm working with a timeline of until end of December for this migration work.

This course of action is no longer being pursued.