MapCompact does not use MC-allocation routines so watermarks are not updated automatically and might become inconsistent.

BUG=http://crbug.com/59688

Review URL: http://codereview.chromium.org/6588007

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6954 ce2b1a6d-e550-0410-aec6-3dcde31c8c00