1243009 - There's no separator between tabs during drag-n-drop if I drag pinned tab and there's overflow in tabs toolbar

Status: RESOLVED WORKSFORME

(Firefox :: Theme, defect)

Description

[arni2033]

>>>   My Info:   Win7_64, Nightly 46, 32bit, ID 20160121030208
STR:
1. Open new tab
2. Open and pin 4 new tabs
3. Open many new tabs to cause overflow in tabs toolbar
4. Drag the 3rd tab to the left:
 4.1. Hover mouse over the 3rd pinned tab (from the start)
 4.2. Hold left mouse button
 4.3. Move mouse pointer to the start of tab list (to the place where 1st tab was displayed)

Result:       There's no separator between 4th tab and new 3rd tab
Expectations: There should be separator

Yet another bug with brand NEW Australis.
I first posted it in bug 1171404 comment 2, but now I know exactly that it's separate issue.
> screencast:   attachment 8649247 [details]