Comment 23 for bug 1189850

This issue happens occasionally, but I don't have a 100% reproducible way to show it. One of the most sucessfull attempts to reproduce it is:

1. make all `speed dial` buttons (previews on about:newtab) in Firefox filled with something reasonably heavy, not plain-text pages (on my machine it is a couple of youtube pages, web interface to SAGE, couple of redmines, etc.)
2. close all tabs except one and this last one tab should be about:newtab page
3. middle-click all the previews as fast as you can one by one, so the pages begin to load in background
3. now hit Ctrl+W till you close everything including that about:newtab page where you've started. You shouldn't wait until all pages you've opened on step 3 are loaded.
4. now open about:newtab again and with a good chance some of the preview will be corrupted. Sometimes there is no corruption, but some preview is displayed on the wrong position, for example two different sites share the same preview image.

Another way to reproduce:

1. make at least one `speed dial` button (preview on about:newtab) in Firefox filled with any kind of preview, just any site you want
2. close all tabs except one and this last one tab should be about:newtab page
3. go to http://www.dreamworksanimation.com/ and add it to bookmarks, then close tab (sorry, bookmarking is the only way I know to make a specific site to show up in previews)
4. open about:newtab again and remove any preview image from it by pressing [X]
5. open bookmarks and drag dreamworksanimation bookmark you've made on step 3 into the freed on step 4 place
6. now visit http://www.dreamworksanimation.com/ so Firefox will generate preview
7. close tab and open again about:newtab. The preview for dreamworksanimation should be corupted

Sorry if the descriptions are a bit messy. Also I don't have any other issues with firefox sites rendering, just issues with rendering previews. I wish there was an easier way to reproduce it.