bug#52385: 29.0.50; Doc-View can't view separate pages in separate windows

[Juri Linkov]

>> But the regression is in overlay window priorities:
>> when two overlays with 'window' properties are added
>> over the same region, then in 27.2 the overlay where
>> the overlay window matches the selected window is preferred
>> over the overlay with another window.  But in 28.0.90
>> the first overlay always wins.
>
> If you don't assign priorities to overlays, you cannot expect any
> particular order of their preferences.  It depends on random factors
> you cannot control.  The window property only filters candidate
> overlays, it doesn't affect their priorities for affecting the
> display.

Sorry for misleading info: actually, it's not about overlay priorities.
When an overlay has the ‘window’ property, then this overlay should apply
only on that window, but currently it's applied to all windows.
So still there is a bug that causes regression.