(Needs 2.21.7) Visual glitches in firefox css transform with SNA accelmethod enabled

[Ivan]

Firefox shows visual glitches in css transform rendering when SNA accelmethod is enabled. With UXA everything works as it should.
Test case: http://jsfiddle.net/tdnLk/4/
Additional details can be found in firefox bug: https://bugzilla.mozilla.org/show_bug.cgi?id=867561

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: xserver-xorg-video-intel 2:2.21.6-0ubuntu4
ProcVersionSignature: Ubuntu 3.8.0-20.31-generic 3.8.11
Uname: Linux 3.8.0-20-generic x86_64
.tmp.unity.support.test.0:

ApportVersion: 2.9.2-0ubuntu8
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: compiz
CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0'
CompositorUnredirectFSW: true
Date: Thu May 9 02:23:52 2013
DistUpgraded: 2013-04-30 22:23:43,578 DEBUG enabling apt cron job
DistroCodename: raring
DistroVariant: ubuntu
DkmsStatus:
 vhba, 20130121, 3.5.0-28-generic, x86_64: installed
 vhba, 20130121, 3.8.0-19-generic, x86_64: installed
 vhba, 20130121, 3.8.0-20-generic, x86_64: installed
ExtraDebuggingInterest: Yes, if not too technical
GraphicsCard:
 Intel Corporation 3rd Gen Core processor Graphics Controller [8086:0166] (rev 09) (prog-if 00 [VGA controller])
   Subsystem: ASUSTeK Computer Inc. Zenbook Prime UX31A [1043:1517]
InstallationDate: Installed on 2012-10-23 (197 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Release amd64 (20121017.5)
MachineType: ASUSTeK COMPUTER INC. UX31A
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=ru_RU.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.8.0-20-generic root=UUID=7221ab10-dceb-475a-899a-687475d63f41 ro quiet splash "acpi_osi=!Windows 2012" pcie_aspm=force drm.vblankoffdelay=1 i915.semaphores=1 vt.handoff=7
SourcePackage: xserver-xorg-video-intel
UpgradeStatus: Upgraded to raring on 2013-04-30 (8 days ago)
dmi.bios.date: 08/28/2012
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: UX31A.214
dmi.board.asset.tag: ATN12345678901234567
dmi.board.name: UX31A
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: 1.0
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: ASUSTeK COMPUTER INC.
dmi.chassis.version: 1.0
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrUX31A.214:bd08/28/2012:svnASUSTeKCOMPUTERINC.:pnUX31A:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnUX31A:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0:
dmi.product.name: UX31A
dmi.product.version: 1.0
dmi.sys.vendor: ASUSTeK COMPUTER INC.
version.compiz: compiz 1:0.9.9~daily13.04.18.1~13.04-0ubuntu1
version.ia32-libs: ia32-libs 20090808ubuntu36
version.libdrm2: libdrm2 2.4.43-0ubuntu1
version.libgl1-mesa-dri: libgl1-mesa-dri 9.1.1-0ubuntu3
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 9.1.1-0ubuntu3
version.xserver-xorg-core: xserver-xorg-core 2:1.13.3-0ubuntu6
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.7.3-0ubuntu2b2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.1.0-0ubuntu2
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.21.6-0ubuntu4
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.7-0ubuntu1
xserver.bootTime: Thu May 9 01:01:32 2013
xserver.configfile: default
xserver.errors:

xserver.logfile: /var/log/Xorg.0.log
xserver.version: 2:1.13.3-0ubuntu6
xserver.video_driver: intel

[Chris Wilson (ickle)]

commit 2217f6356b53263b6ce8f92b5c29c0614d4ef2a5
Author: Chris Wilson <email address hidden>
Date: Thu May 9 13:46:11 2013 +0100

    sna/trapezoids: Fix the determination of the trapezoid origin

    "src-x and src-y register the pattern to
    the floor of the top x and y coordinate of the left edge of the
    first trapezoid,"

    Bugzilla: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/1178020
    Signed-off-by: Chris Wilson <email address hidden>