Windows change workspaces when screen size or orientation changes

[cybersphinx]

I have a Thinkpad X61 Tablet with a rotating 1400x1050 screen, though I assume similar things happen when rotating desktop monitors with different resolutions.

Steps to reproduce:
- Run Unity with 3x3 workspaces, let's call them
  1 2 3
  4 5 6
  7 8 9
- Run one maximized program (terminal, for demonstration purposes) on each workspace.
- Run "xrandr -o left" in the top left workspace.

Expected:
- The nine windows stay on the workspaces they are on.

Behaviour:
- The windows in workspaces 3, 6, 7, 8, 9 get moved to workspaces 1, 2, 4, 5, destroying the previous window arrangement.
- After running "xrandr -o normal" to reset the screen orientation the windows still keep their new workspaces.
- Rotating the screen again, this time in the bottom right workspace, moves all the windows to workspaces 2 and 3. Rotating it back moves them again, to 8 and 9.

This makes using workspaces to arrange programs spatially pretty much unusable when you also want to rotate the screen occasionally.

Since 3x3 workspaces are not the default, here's presumably the same problem with the default 2x2 workspaces:
- Run Unity with 2x2 workspaces.
- Run one maximized terminal in each of the four workspaces.
- Run "xrandr -s 640x480" in the top left workspace's terminal.

Expected:
- The four terminals stay on the four workspaces they are on.

Behaviour:
- The four terminals are all moved to the top left workspace, destroying the previous window arrangement.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: unity 5.14.0-0ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-29.46~ppa1-generic-tuxonice 3.2.24
Uname: Linux 3.2.0-29-generic-tuxonice x86_64
ApportVersion: 2.0.1-0ubuntu12
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]
Date: Sun Aug 19 15:57:06 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
SourcePackage: unity
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

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