1216210 - UI appears blacked out after dragging a tab outside the window

Status: NEW

Description

[Anthony Hughes (:ashughes) [QA]]

After dragging a tab outside the main browser window I saw areas of the UI get blacked out (will attach screenshots). Dragging the tab back to the main window showed a different blackout symptom. Dragging the tab back to its own window resulted in everything being corrected. 

FWIW, I am using a Macbook Pro (Retina, 13-inch, Late 2013) with OS X 10.11.1 Beta (15B30a) and Firefox Nightly 44.0a1. I have connected a Dell U2410 1080p monitor via Thunderbolt/HDMI and all Firefox windows are on this second screen.

As of yet this issue is not reproducible.

Steps:
1) Have one Firefox window open with multiple tabs, in my case:
> Fastmail (pinned), Mozilla Wiki (pinned), IRCCloud (pinned), MDN, Mozilla Wiki, Mozilla Wiki, QMO, Google Docs
2) Move the window to a secondary monitor, in my case:
> Dell U2410 @ 1920x1080 connected via Thunderbolt:HDMI adapter
3) Drag the Google docs tab to the desktop
> Google docs tab opens in its own window (see screenshot A)
4) Drag the Google docs tab back to the main window
> Google docs tab returns to the main window (see screenshot B)
5) Drag the Google docs tab back to the desktop
> Google docs tab opens in its own window without issue

Result:
Black screen issues as described above and illustrated in the screenshots.

Expected Result:
No black screen issues should be present.

Graphics Information:
>           Asynchronous Pan/Zoom     wheel input enabled
>                       Device ID     0x0a2e
>         GPU Accelerated Windows     2/2 OpenGL (OMTC)
> Supports Hardware H264 Decoding     No
>                       Vendor ID     0x8086
>                  WebGL Renderer     Intel Inc. -- Intel Iris OpenGL Engine
>        windowLayerManagerRemote     true
>              AzureCanvasBackend     skia
>             AzureContentBackend     quartz
>      AzureFallbackCanvasBackend     none
>            AzureSkiaAccelerated     1

Comment 1

[Anthony Hughes (:ashughes) [QA]]

Created attachment 8675783 [details]
Screenshot A: tab dragged out

Comment 2

[Anthony Hughes (:ashughes) [QA]]

Created attachment 8675784 [details]
Screenshot B: tab dragged back

Comment 3

[Jeff Gilbert [:jgilbert]]

Anything interesting here?

Comment 4

[Jeff Muizelaar [:jrmuizel]]

Have you seen this again?

Comment 5

[Anthony Hughes (:ashughes) [QA]]

(In reply to Jeff Muizelaar [:jrmuizel] from comment #4)
> Have you seen this again?

Yes, I can reproduce it easily in today's Nightly.