Clicking such a link opens a new tab. The compositor was briefly in charge of drawing the root layer while the backing store was inactive and the user was looking at the other tab. The problem was that the compositor believed it was still painting the root layer even after the backing store became active again. The flag was not properly cleared when turning off compositing. Fixed by returning false from drawsRootLayer() if we don't have a root layer. Reviewed internally by Filip Spacek.
Created attachment 144225 [details] Patch
Comment on attachment 144225 [details] Patch Clearing flags on attachment: 144225 Committed r118625: <http://trac.webkit.org/changeset/118625>
All reviewed patches have been landed. Closing bug.