Drag & drop of vertical tabs forces a tab selection/page load

[stephendonner]

Description

Drag & drop of vertical tabs forces a tab selection/page load

Found while testing #29692

Steps to Reproduce

1. install 1.52.57
2. launch Brave
3. enable Use vertical tabs if not already
4. load any website and context-click on its tab
5. choose Use vertical tabs
6. open 5 or more tabs (just makes it easier to drag & drop)
7. select any tab
8. wait for it to load
9. click on and start dragging any other tab
10. notice which tab/page you're on

Actual result:

Even though it seemed to sense a click + hold to initiate a drag, it still forced selection on the other tab, causing it to load

Expected result:

Maybe a timer, or wait until mouseDown or something, to key in the tab selection, rather than continue the drag operation?

Reproduces how often:

100%

Brave version (brave://version info)

Brave	1.52.57 Chromium: 112.0.5615.138 (Official Build) nightly (x86_64)
Revision	2258f2fcaeb07bc95c992b7ca47f0b43ead9865c-refs/branch-heads/5615@{#1282}
OS	macOS Version 13.4 (Build 22F5037d)

Version/Channel Information:

• Can you reproduce this issue with the current release? No
• Can you reproduce this issue with the beta channel? Yes
• Can you reproduce this issue with the nightly channel? Yes

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields?
• Does the issue resolve itself when disabling Brave Rewards?
• Is the issue reproducible on the latest version of Chrome?

Miscellaneous Information:

/cc @sangwoo108 @simonhong @brave/qa-team @rebron @bsclifton

[sangwoo108]

If I understand this correctly, this behavior is the same with the horizontal tab strip. Based on the upstream implementation, tab selection changes on mouse down, not on mouse release. So it might be better to label this as feature/tabs-bar. But I think changing this behavior would bring quit a lot of new problems.