It should be noted that this bug is basically an experiment. This patch will require a fair amount of testing before I'm convinced that it's a good idea to replace the current heuristics with these ones.
Created attachment 149901 [details]
work in progress
Just putting up for EWS. Not ready for review yet.
Created attachment 150032 [details]
Landed in http://trac.webkit.org/changeset/121511
Rolled out in http://trac.webkit.org/changeset/122182
It made in-browser V8v7 10% slower.
Relanded in http://trac.webkit.org/changeset/122206