Tab scroll bar is cannot be dragged

[Arctomachine]

Captchas

• I have read the instructions.
• I have searched existing issues and avoided creating duplicates.
• I am not filing an enhancement request.

What happened?

Although tab scroll bar reacts to hovering cursor same as window scroll bar, it cannot be dragged.
Doing so results in dragging whole window instead of scrolling tabs list.

Reproducible?

• I have checked that this issue cannot be reproduced on Mozilla Firefox.

Version

1.7.4b

What platform are you seeing the problem on?

Windows

Relevant log output if applicable