Rollback of r13152 in trunk branch.

Let marking speed depend on the actual incremental write barrier count.

R=jkummerow@chromium.org
BUG=

Review URL: https://codereview.chromium.org/11464022

git-svn-id: http://v8.googlecode.com/svn/trunk@13173 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
2 files changed