Checkbox tree of wizard to start a resource negotiation doesn't expand to show initial selection in older Eclipse versions

[tobous]

When opening the wizard to start a resource negotiation with pre-selected resources, the contained checkbox tree should be expanded to that all pre-selected base resources are visible. The logic for this behavior is in place, but it does not seem to function correctly in older Eclipse versions.

This issue is reproducible in Eclipse Photon (4.8.0) but is no longer reproducible in Eclipse 2019-9-R, so it has to have been fixed by Eclipse somewhere in-between.

I am not sure whether there is anything we can do about this if this is purely an upstream issue. This could be related to bug 74415. The proposed workaround of expanding first and selecting afterwards does not seem to work.

I mainly tested this with my rework of the wizard done in #1035, but it should also work with the previous wizard (if it contains logic to expand the tree to a specific level).

This issue does not seem to be OS specific as I was able to reproduce this under Linux and Window.

Steps to Reproduce

Requires the reworked wizard introduced in #1035.

1. Connect to an XMPP account.
2. Select a non-project folder in the project view (e.g. a src folder). Anything besides a project is fine (since projects are always visible by default and don't require any expansion).
3. Right-click the folder and select "Share Resource(s)..."

Expected Behavior

The checkbox tree is expanded to show the selected folder. The entry for the folder is checked.

Actual Behavior

The checkbox tree is completely collapsed, only showing the project entries. (The folder entry is still selected and can still be manually expanded to.)