Take survival rates of young objects into account when choosing old generation limits.

Take survival rates of young objects into account when choosing old generation limits.

Stable high survival rates of young objects both during partial and
full collection indicate that mutator is either building or modifying
a structure with a long lifetime.

In this case we aggressively raise old generation memory limits to
postpone subsequent mark-sweep collection and trade memory space
for the mutation speed.

Review URL: http://codereview.chromium.org/2809032

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4938 ce2b1a6d-e550-0410-aec6-3dcde31c8c00