Configure platforms with swap memory with larger heap size by default. Also
introduce an additional "bucket" between 1GB-2GBs.

BUG=None
R=hpayer@chromium.org, jkummerow@chromium.org

Review URL: https://codereview.chromium.org/24978006

Patch from Ross McIlroy <rmcilroy@chromium.org>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17081 ce2b1a6d-e550-0410-aec6-3dcde31c8c00