Currently we still use the GC machinery to get an exclusive access to the prototype chain when setting a prototype. I suggest to remove that. The only drawback AFAICS is that it would be not possible to implement a thread-shared object with script-mutable prototype. But given the current plans it is rather unlikely that we would need to support such object.
Created attachment 533953 [details] [diff] [review] v1 Straightforward implementation
Comment on attachment 533953 [details] [diff] [review] v1 Looks perfect. Thanks.
cdleary-bot mozilla-central merge info: http://hg.mozilla.org/mozilla-central/rev/dbe681ddbd5b