Switcher not shown on multiple monitor config

[Impact]
When using a multi-monitor config, the alt-tab switcher was not shown, but functioned as if it was.

[Test Case]
From unity/manual-tests/Switcher.txt:
Multi-monitor Alt-Tab
---------------------
This test only applies for multiple monitor.
App names here are an example, any apps will do.

Setup:
#. Start with no apps open (or at least remember what is open where)
#. Start terminal on workspace 1
#. Start firefox on workspace 2
#. Move to workspace 2

Scenario 1: Perform on workspace 1
Scenario 2: Perform on workspace 2

Actions:
#. Hold Alt, press tab
#. Observe
#. Release Alt

Expected Result:
Scenario 1:
  Terminal is shown in the alt-tab switcher, but firefox on workspace 2 is not.
Scenario 2:
  Firefox is shown in the alt-tab switcher, but the terminal on workspace 1 is not.

[Observed Result]
The switch was not shown.

[Packages under test]
From ppa:unity-team/release:
 - bamf - 0.2.122+bzr482ubuntu0+437
 - compiz - 1:0.9.8.0-0ubuntu1~test8
 - nux - 3.2.0+bzr651ubuntu0+361
 - unity - 6.2.0+bzr2633ubuntu0+762

[Hardware config]
Nvidia hardware with nouveau driver.

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: unity 6.2.0+bzr2633ubuntu0+762 [origin: LP-PPA-unity-team-release]
ProcVersionSignature: Ubuntu 3.5.0-13.14-generic 3.5.3
Uname: Linux 3.5.0-13-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.5.1-0ubuntu3
Architecture: amd64
CompizPlugins: [core,composite,opengl,compiztoolbox,decor,vpswitch,snap,mousepoll,resize,place,move,wall,grid,regex,imgpng,session,gnomecompat,animation,fade,unitymtgrabhandles,workarounds,scale,expo,ezoom,unityshell]
CrashDB: unity
Date: Thu Aug 30 11:28:25 2012
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Alpha amd64 (20120627)
ProcEnviron:
 TERM=xterm
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: unity
UpgradeStatus: No upgrade log present (probably fresh install)