Refactor some entry point stuff. BUG=angleproject:747 Change-Id: I80634b5e6de8bae1433c49a56a92d3b19c24e11d Reviewed-on: https://chromium-review.googlesource.com/395568 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>