[Bug 41175] New: Firefox tooltips are partly black

https://bugs.winehq.org/show_bug.cgi?id=41175

Bug ID: 41175
           Summary: Firefox tooltips are partly black
           Product: Wine
           Version: 1.9.17
          Hardware: x86
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: user32
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

It reproduces 100% of time if you follow these steps:

1. Hover over toolbar "Menu" button (the identity sign ≡), see "Open menu"
tooltip
2. Move cursor to Downloads button (the down-pointing arrow), see
"Display p████████████████████████████" (instead of "Display progress of
ongoing downloads"). Notice that the non-black rectangle is the same as was in
previous tooltip ("Open menu").
3. Try opening any other menu or tooltip — it only has that original rectangle
of "Open menu" tooltip drawn, with other parts black.

In some cases jumping to another submenu clears the blackness, and a bigger
rectangle becomes visible on all menus for a while.

Tested on Firefox 47 and 48.