We only seem to force scavenge in our cctest test suite, so this is
expected to fix some flakiness in our tests, but it will not
improve stability of v8 itself.

R=hpayer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/167423004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19460 ce2b1a6d-e550-0410-aec6-3dcde31c8c00