Created attachment 861775 [details] screenshot Under Fedora 20 and gnome-shell 3.10.3 I get hit by 100% cpu consumption every now and then. Sadly you don't realize it until you do some other operations that require heavy cpu usage. I am worried to leave the machine on because I am worried that this behaviour could cause damage to CPU after a while. Attached a Screenshot with TOP showing the issue.
The times I've poked it with gdb, it's always been somewhere running JavaScript code.
Does pressing Alt-F2 + r make this better for a short while as reported on Bug 911926? How many monitors do you have? (Bug 1060057 reports 3; not sure if these are the same problem or if the number of displays matters.)
Looks like most recent versions of packages have solved this issue. Never happened again.