Collect garbage before serializing heap in test-serialize
Collect garbage before serializing heap in test-serialize

BUG=none
TEST=nosnap bots with i18n enabled are happy
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/24196004

git-svn-id: b158db1e4b4ab85d4c9e510fdef4b1e8c614b15b@16826 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh