RFR: [WIP]8209788: Left/Right/Ctrl+A keys not working in editor of ComboBox if popup showing

[Kevin Rushforth]

On Sat, 11 Apr 2020 09:53:46 GMT, Ambarish Rapte <arapte at openjdk.org> wrote:

> The issue occurs because the key events are consumed by the `ListView` in `Popup`, which displays the items.
> This is a regression of [JDK-8077916](https://bugs.openjdk.java.net/browse/JDK-8077916). This change aadded several
> `KeyMapping`s for focus traversals to `ListView`, which consume the `Left`, `Right` and `Ctrl+A` key events.
> Fix:
> 1. Remove the four focus traversal arrow `KeyMapping`s from `ListViewBehavior`.
> 2. Add the `Ctrl + A` `KeyMapping` to `ListViewBehavior` only if the `ListView`'s selection mode is set to
> `SelectionMode.MULTIPLE`.  `ComboBox` uses the `ListView` with `SelectionMode.SINGLE` mode.
> Change unrelated to fix:
> `ComboBoxListViewBehavior` adds `KeyMapping` for `Up` and `Down` keys, which are not invoked when the `ComboBox` popup
> is showing. When the popup is shown, the Up and Down key events are handled by the `ListView` and the `KeyMapping` code
> from `ComboBoxListViewBehavior` does not get executed. These KeyMapping are removed. However this change is not needed
> for the fix. But this seems to be dead code.   Verification:
> Added new unit tests to verify the change.
> Also verified that the behavior ListView behaves same before and after this change.

Once the merge conflicts and review comments are addressed, I'll put this back on my review queue.

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PR: https://git.openjdk.java.net/jfx/pull/172