[alt-tab] Down arrow shouldn't work if only one window of an app is open

[Jeremy Bícha]

The down arrow shortcut to show multiple windows of the same app should not work if there is only one window of that app open.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: unity 4.8.0-0ubuntu1
ProcVersionSignature: Ubuntu 3.0.0-8.10-generic 3.0.1
Uname: Linux 3.0.0-8-generic x86_64
Architecture: amd64
CompizPlugins: [core,bailer,detection,composite,opengl,decor,mousepoll,vpswitch,regex,animation,snap,expo,move,compiztoolbox,place,grid,imgpng,gnomecompat,wall,ezoom,workarounds,resize,fade,unitymtgrabhandles,scale,session,unityshell]
Date: Fri Aug 12 16:19:13 2011
InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Release amd64 (20101007)
SourcePackage: unity
UpgradeStatus: Upgraded to oneiric on 2011-06-17 (56 days ago)