In CSA::AllocateRaw, ensure that the given allocation size fits into a
Smi.

Bug: chromium:848672
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I4e74791296163188b1ca77cae8226a9833fba8ef
Reviewed-on: https://chromium-review.googlesource.com/1084930Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53495}