The size of a snapshot is now 65-80% of the JS heap size (tested on
GMail and Wave), previously it was >200%.

BUG=783

Review URL: http://codereview.chromium.org/3060008

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@5211 ce2b1a6d-e550-0410-aec6-3dcde31c8c00