Merged r13072 into trunk branch.

Allow incremental marking when expose_gc is turned on.

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/11419201

git-svn-id: http://v8.googlecode.com/svn/trunk@13075 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
4 files changed