Dragging sections in sidebar only changes cursor on hover which causes incorrect cursor display

[DannyJJK]

• VSCode Version: Code 1.17.2 (b813d12, 2017-10-16T13:47:41.889Z)
• OS Version: Darwin x64 17.3.0
• Extensions:

Extension	Author (truncated)	Version
output-colorizer	IBM	0.1.2
material-icon-theme	PKi	2.2.4
code-settings-sync	Sha	2.8.5
sort-lines	Tyr	1.3.0
quokka-vscode	Wal	1.0.75
path-intellisense	chr	1.4.2
githistory	don	0.2.3
tslint	eg2	1.0.14
vscode-npm-script	eg2	0.3.3
php-intellisense	fel	1.5.4
code-runner	for	0.8.3
docthis	joe	0.6.0
ftp-sync	luk	0.3.3
theme-monokai-pro-vscode	mon	1.1.2
vscode-apache	mrm	1.1.1
cpptools	ms-	0.14.0
csharp	ms-	1.12.1
typescript-javascript-grammar	ms-	0.0.24
vscode-code-outline	pat	0.0.12
stylelint	shi	0.30.0
vscode-coffeelint	slb	0.0.2
language-stylus	sys	1.8.0
es-quotes	vil	0.2.6
vscode-todo-highlight	way	0.5.11
twig	wha	1.0.2
vscode-import-cost	wix	2.5.1

(5 theme extensions excluded)

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Steps to Reproduce:

1. Have multiple sections on sidebar (e.g. workspace, commits, compare commits). I also have the code outline plugin which creates another section.
2. Place the cursor at the very bottom of the draggable area for that section, then hold down the mouse and drag downwards. If done at the right speed, the cursor and UI should be out of sync, which causes the incorrect cursor to display

Suggested fix:
Cursor should change not only on the hover event, but also when the mouse button is held-down on the dragging area. This would prevent the cursor flickering
cursorbug.mov.zip

I've attached a video showing the issue. The video is in MOV format since that's all QuickTime lets me export as.

[sandy081]

@joaomoreno Shall we have a new label for view/split view related issues?

Edit: I see there is already a label workbench-layout where some of the view related issues are labelled. Use that?

[joaomoreno]

Usually I just put workbench.

[joaomoreno]

@DannyJJK Would you like to fix this in a PR?

[bpasero]

Usually I just put workbench.

Please don't.

[joaomoreno]

@bpasero Why don't you delete the label?

[bpasero]

@joaomoreno it is still useful as workbench inbox tracker because the bot is assigning to me when using this label and then I go on and put the right labels.

[bpasero]

Duplicate of #21675