[regression] Mouse hotbuttons broken on non-topmost windows

[Chow Loong Jin]

On windows that are not topmost, or at least not the topmost window after "Always On Top" windows, scrollwheel based hotkeys do not work, for example, Alt+wheel for changing window opacity, or Super+wheel for zooming in/out.

Steps to reproduce:
1. Open a nautilus window. Leave it unmaximized.
2. Open another nautilus window. Leave it unmaximized as well.
3. Click on the second window to make sure it's raised.
4. Move mouse over the second window, and use Super+ScrollUp to zoom in using the ezoom plugin (this should work, otherwise check to make sure the ezoom plugin is enabled). Zoom back out (Super+ScrollDown) when you have verified that this works.
5. Move mouse over the first window, but do not click it, and leave it below the second window.
6. Attempt to use Super+ScrollUp to zoom in. Notice that it doesn't work.
7. Click on the first window to raise it, then Try step 6 again. Notice that it works now.

Additional steps with always-on-top window:
8. Click on the second window again to raise it.
9. Right click on the window title bar and enable the "Always on top" option.
10. Click on the first window. The second window should remain on top.
11. Attempt step 6 again. Notice that the hotbutton works now.

Hotbuttons verified not to work:
1. Super+Scroll for zooming
2. Alt+Scroll for changing opacity
3. Ctrl+Alt+Scroll for changing desktop (this is a local customization)

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: compiz 1:0.9.11+14.04.20140409-0ubuntu1
Uname: Linux 3.14.0-hyper1 x86_64
.tmp.unity.support.test.0:

ApportVersion: 2.14.1-0ubuntu2
Architecture: amd64
CompizPlugins: [core,composite,opengl,copytex,compiztoolbox,decor,vpswitch,extrawm,text,resize,ring,screenshot,place,commands,put,mousepoll,move,gnomecompat,annotate,blur,clone,widget,regex,imgpng,animation,obs,workarounds,neg,bicubic,resizeinfo,grid,expo,session,wall,showmouse,ezoom,unitymtgrabhandles,fade,scale,scalefilter,showdesktop,scaleaddon,unityshell]
CompositorRunning: compiz
CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0'
CompositorUnredirectFSW: true
CurrentDesktop: Unity
Date: Wed Apr 16 16:10:17 2014
DistUpgraded: 2014-03-03 20:19:00,072 DEBUG enabling apt cron job
DistroCodename: trusty
DistroVariant: ubuntu
DkmsStatus:
 tp-smapi, 0.41, 3.13.0-24-generic, x86_64: installed
 tp-smapi, 0.41, 3.14.0-hyper1, x86_64: installed
GraphicsCard:
 Intel Corporation 3rd Gen Core processor Graphics Controller [8086:0166] (rev 09) (prog-if 00 [VGA controller])
   Subsystem: Lenovo Device [17aa:21fa]
MachineType: LENOVO 2325F45
PackageArchitecture: all
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.14.0-hyper1 root=/dev/mapper/cryptostuff-root ro "acpi_osi=!Windows 2012" i915.i915_enable_rc6=7 i915.lvds_downclock=1 i915.i915_enable_fbc=1 i915.semaphores=1 rootflags=data=writeback splash resume=/dev/mapper/cryptostuff-swap crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M crashkernel=384M-:128M vt.handoff=7
SourcePackage: compiz
UpgradeStatus: Upgraded to trusty on 2014-03-03 (43 days ago)
dmi.bios.date: 04/30/2013
dmi.bios.vendor: LENOVO
dmi.bios.version: G2ET94WW (2.54 )
dmi.board.asset.tag: Not Available
dmi.board.name: 2325F45
dmi.board.vendor: LENOVO
dmi.board.version: Not Defined
dmi.chassis.asset.tag: RH0005026
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvrG2ET94WW(2.54):bd04/30/2013:svnLENOVO:pn2325F45:pvrThinkPadX230:rvnLENOVO:rn2325F45:rvrNotDefined:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 2325F45
dmi.product.version: ThinkPad X230
dmi.sys.vendor: LENOVO
version.compiz: compiz 1:0.9.11+14.04.20140409-0ubuntu1
version.ia32-libs: ia32-libs 20090808ubuntu36
version.libdrm2: libdrm2 2.4.52-1
version.libgl1-mesa-dri: libgl1-mesa-dri 10.1.0-4ubuntu5
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 10.1.0-4ubuntu5
version.xserver-xorg-core: xserver-xorg-core 2:1.15.1-0ubuntu1
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.8.2-1ubuntu2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.3.0-1ubuntu3
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.910-0ubuntu1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.10-1ubuntu2
xserver.bootTime: Mon Apr 14 14:16:27 2014
xserver.configfile: default
xserver.errors:

xserver.logfile: /var/log/Xorg.0.log
xserver.outputs:
 product id 4204
 vendor AUO
xserver.version: 2:1.15.0-1ubuntu7

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.