Here's a rough translation of a tweet by @xharaken.
"Space rays hit computers and mess up the bits in the memory" "hardware bugs mess up the bits in the memory" such things almost never happen, but they happen on a nearly daily basis when there are so many users using a software like [Google] Chrome. So the GC running inside Chrome has a function to check such bit anomalies.
I do understand that such weird errors happen, but I don't understand how or why checking such errors is important in writing a garbage collector. What I thought was the job of garbage collectors have nothing to do with data integrity in the memory. Think about it - what a garbage collector does is it wipes data in the memory that are no longer referenced. Weird bugs caused by random memory bugs is not in a, at least, say, obvious way, related to a garbage collector's job.