Version 3.28.71.1 (merged r23084)

Old space cannot be assumed to be iterable between GCs, even if swept precisely.

BUG=
TBR=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/462093002

git-svn-id: https://v8.googlecode.com/svn/trunk@23085 ce2b1a6d-e550-0410-aec6-3dcde31c8c00