This upgrade also introduces exact stack rooting (see to the wiki:
JSRootingGuide) and fixes problems with moving GC. This allows us to
enable generational garbage collection (GGC).
Measurements a few months ago have shown a performance improvement of a
non-visual replay of around 13.5%. This probably varies quite a bit, but
it should be somewhere between 5-20%. Memory usage has also been
improved. Check the forum thread for details.
Thanks to everyone from the team who helped with this directly or
indirectly (review, finding and fixing issues, the required C++11
upgrade, the new autobuilder etc.)! Also thanks to the SpiderMonkey
developers who helped on the #jsapi channel or elsewhere!
Fixes#2462, #2415, #2428, #2684, #1374
Refs #2973, #2669
This was SVN commit r16214.
