[JeffryBooher]

This is for #9439 -- Clicking on items in the working set is slow.

• Don't create the drag ghost until needed
• Improve Pane.focus(one big drag was currentElement.blur() so we only need to do that if we're focusing something that isn't code mirror.
• Improve EditorManager._showEditor(), the UX changes for the pane DOM weren't targeting the right node to see if it needed to re-add the editor to the pane so this was happening every time the editor was shown.
• Improve _open and _edit to not activate pane until after opening the document

Also fixes #9428

[JeffryBooher]

@redmunds fixed failing unit test. This was also pointing to opening a project and the focus looked like it was in the editor but it really wasn't.

[JeffryBooher]

Ready for review.

[redmunds]

$("#working-set-list-container") is already stored in $workingFilesContainer, so no need for another lookup.

[redmunds]

Done with code review. Behavior feels solid. All tests pass. Just a few comments.

[JeffryBooher]

@redmunds ready for another review

[TomMalbran]

Nit: There is a @ instead of *.

[redmunds]

This call to _edit() ignores the original options object that was passed in. These settings should instead be set on the original options object so that any other settings get passed through. Even if these are currently the only 2 possible options, some new ones might be added some day.

[redmunds]

Done with review. A few more comments.

[JeffryBooher]

@redmunds @TomMalbran thanks for the review! Let me know if it needs any further work before merging

[redmunds]

@JeffryBooher I just noticed a weird dragging case:

1. Open in Split View (I'm using Vertical)
2. Open a few files in upper (Left) working set
3. Open 12-15 files (enough for a fair amount of scrolling) in lower (Right) working set
4. Scroll lower working set all the way to bottom
5. Start dragging last item upward until you hit top of working set...

Results
If you drag fast enough, you can easily drag it to upper working set. If you drag slower, item gets "stuck" in area at top of working set that triggers auto-scrolling. If mouse keeps moving up while item is "stuck" (and list is auto-scrolling), then item is no longer under mouse (but you still have capture)!