Description:
When trying to drag and drop an image in chromium, a small preview of the image appears and follows the mouse, but the rectangle where was the first image of the preview becomes a "graphical artefact", I mean that the image stay there even when you change of tab, of application, of workspace, etc.
This artefact disappear when chromium is closed.

Additional info:
I'm on x86_64, and I use the proprietary graphics driver nvidia.

My system is up to date (and I use [testing]).

$ pacman -Qi chromium | grep Version
Version : 5.0.375.127-1
$ pacman -Qi nvidia | grep Version
Version : 256.53-1

I tested with a new profile for chromium (chromium --user-data-dir=/tmp/chromium) but the problem is still there.

Steps to reproduce:
- Go to a webpage where there are images (<img>), for example [1], with chromium
- Drag and drop the image
- Open a new tab, or a new application, or go to another workspace

Here is a screeshot of the bug [2]

[1] : http://en.wikipedia.org/wiki/File:Panorama_of_the_Fountain_of_Time.JPG
[2] : http://img819.imageshack.us/img819/2599/201009011639021600x900s.png