[cmv3] Mac w/mouse - scrollbars appear incorrectly in inline editors

[gruehle]

Steps to repro

1. Plug a mouse into your mac
2. Launch Brackets, and open the brackets src folder. Make sure the Brackets window is not too wide.
3. Open brackets.js
4. On ~line 156, put the cursor in setEditorHolder and press Cmd-E. Inline editor opens and a horizontal scrollbar appears in editor (if the horizontal scrollbar isn't visible, make the window narrower until it is shown).
5. Scroll down to the bottom of the file
6. Scroll back up and look at the inline editor

Results
The inline editor show an empty vertical scrollbar, no horizontal scrollbar, and the line numbers are indented to the right.

Expected
Inline editor should look the same as when it was first opened.

[njx]

Reviewed. To me for sprint 20. Potentially deferrable if it's risky to fix.

[RaymondLim]

I can reproduce it on Windows with the following steps.

1. Open index.html from Getting Started project.
2. Set cursor on h1 tag and press Ctrl+E to open inline editor.
3. Drag the vertical scroll bar down and then up. (or you can use Ctrl+End, then Ctrl+Home in main editor.)

Now you see an empty scroll bar inside the inline editor and line numbers inside the inline are drawn over the content of inline editor.

[njx]

Similar to my comment in #2782, we already have code that's supposed to handle refreshing the child editor when a widget gets re-added to the DOM. Perhaps there's a similar underlying bug going on here.

[njx]

Aha. It looks like the underlying issue is codemirror/codemirror5#1226. I have a workaround.

[gruehle]

Confirmed fixed. Closing.